What is a bond?

When you buy a share, you become a tiny part-owner of a business. A bond is the other great way of putting money to work, and it flips that idea on its head: instead of owning a slice of a company, you lend money to one — or to a government — and they pay you for the privilege. It is one of the oldest financial ideas there is, and understanding it makes the news about "interest rates" and "government debt" suddenly make sense.

Let us build the picture from the ground up, using nothing more complicated than the idea of lending a friend a tenner.

A bond is a loan with a receipt

Imagine a government wants to build a hospital but does not have the cash to hand. It needs to borrow. Rather than walking into a single bank, it borrows a little from thousands of investors at once by issuing bonds. Each bond is a promise printed on paper (these days, held electronically) that says three things:

• How much you lent — the "face value", say £1,000.
• How much interest they will pay you each year while they hold your money — the coupon.
• The date they will give your original money back — the maturity.

That is the entire deal. You hand over £1,000 today; they pay you a fixed amount every year; and on the maturity date they return your £1,000. A bond is, quite literally, an IOU you can hold, sell, or pass on — a receipt for a loan.

What the coupon really means

The coupon is just the interest rate, fixed at the moment the bond is created. A £1,000 bond with a 4% coupon pays £40 a year, every year, until it matures. It does not wobble with the company's profits or the mood of the market — that fixed, predictable stream is the whole appeal.

The word "coupon" is a lovely historical leftover. Old paper bonds came with a strip of little detachable tickets around the edge. Each year you would physically clip off a coupon and post it in to claim your interest. The paper tickets are long gone, but the name stuck — which is why you will still hear bond interest called the coupon.

Bonds versus shares: owner or lender?

This is the single most useful distinction to hold in your head. A share and a bond are two completely different relationships with a company.

• A shareholder is an owner. If the business soars, your share can be worth many times what you paid. If it sinks, no one owes you a penny back. Your upside is huge and your downside is real.
• A bondholder is a lender. You are owed a fixed set of payments and your money back on a set date — and that is all. It does not matter whether the company triples in size or merely trundles along; your £40 a year is the same either way.

So bonds trade away thrills for reliability. A shareholder in a wildly successful company might see their money grow tenfold; a bondholder in that same company just gets their agreed coupon and their capital back. In exchange, the bondholder sleeps more soundly. If the business runs into trouble, lenders are paid before owners — so bonds usually sit lower on the ladder of danger than the same company's shares. It is a classic case of the risk and reward trade-off in action: less to fear, but also less to dream about.

Why a bond's price moves — even though the coupon is fixed

Here is the part that surprises everyone. The coupon never changes, yet a bond's price most certainly does, because bonds can be bought and sold before they mature. The key to all of it is a see-saw: when general interest rates go up, existing bond prices go down, and vice versa.

Picture why. You own a bond paying a 4% coupon. Tomorrow, interest rates rise and brand-new bonds are issued paying 6%. Nobody now wants your stingy 4% bond at full price when they could buy a fresh 6% one instead. To sell yours, you have to drop the price until the return works out roughly the same as the new bonds. Your coupon did not move — the world around it did.

The reverse is just as true. If rates fall to 2%, your 4% bond is suddenly a prize, and buyers will happily pay more than face value to get that above-average income. This tug-of-war between fixed coupons and shifting interest rates is why bonds, often thought of as "boring and safe", still have prices that rise and fall day to day.

Government bonds and company bonds

Broadly, bonds come from two kinds of borrower, and the difference is all about trust.

Government bonds are loans to a country. In the UK these are nicknamed gilts; in the US, Treasuries. A stable government is considered extremely likely to pay you back — it can, after all, raise taxes — so these are treated as some of the safest investments around. Because the risk is low, the interest they offer is usually modest.

Corporate bonds are loans to companies. A company can, in a bad year, fail to pay — so to tempt lenders, companies generally offer a higher coupon than a government would. The shakier the company, the higher the interest it must dangle to persuade anyone to lend. A rock-solid household name pays only a little above the government rate; a struggling firm has to pay a lot more. That extra interest is simply the price of taking on extra risk.

Where bonds fit in a sensible mix

Bonds matter to ordinary investors mainly as a steadying weight. Shares and bonds often behave differently in the same conditions: when nervous markets send share prices tumbling, investors frequently rush into safe government bonds, pushing their prices the other way. Holding some of each means the two can partly cushion one another, so your total value swings around less. That is the heart of diversification — not putting everything into one type of thing that all rises and falls together.

Bonds are not risk-free, though, and it is worth being honest about their weak spot. Because a bond's income is fixed, inflation is its natural enemy: if prices in the shops rise faster than your 4% coupon, the money you get back buys less than the money you lent. A "safe" bond that pays 3% while inflation runs at 5% is quietly losing you purchasing power. Safety from one danger is not safety from all of them.

Seeing it for yourself, risk-free

The neat thing about learning this stuff is that you do not need real money to feel how it works. In the Student Investor Challenge you run a virtual £100,000 portfolio and watch, in real time, how different kinds of holdings behave. You will notice how racy company shares can leap and lurch while steadier holdings barely twitch — the same contrast that sits between a risky share and a safe bond. Teams that climb the league table over a season tend to grasp why balance matters, and understanding bonds is a big part of understanding what "balanced" even means. Learning it with pretend money is about the cheapest financial education going.

FAQ

What is a bond in simple terms?

A bond is a loan you make to a government or a company. In return they promise to pay you regular interest for a set number of years, and then hand your original money back on an agreed date. You are the lender, not an owner, so a bond is essentially a written IOU that can be bought and sold.

What is the difference between a bond and a share?

A share makes you a part-owner of a company, so you share in its success and its failures with no promise of getting your money back. A bond makes you a lender: you are owed a fixed stream of interest and your capital back on a set date, whether the business booms or just plods along. Shares offer more upside and more risk; bonds offer steadier, capped returns.

What is a coupon on a bond?

The coupon is the fixed interest a bond pays each year, written as a percentage of the bond's original face value. A £1,000 bond with a 4% coupon pays £40 a year until it matures. The name is a leftover from the days when paper bonds had physical coupons you clipped off and posted in to claim each payment.

Why do bond prices go up and down?

A bond's interest payment is fixed, but the price you pay to buy the bond can change as it trades. When general interest rates rise, older bonds paying less become less attractive, so their price falls until the return matches new bonds. When rates fall, existing higher-paying bonds become more valuable, so their price rises. Prices also move if lenders worry the borrower might not repay.