Can someone explain an ISA to me?

It's a savings account, where you don't pay tax on the interest. So no income tax, no capital gains tax, you don't need to report it to HMRC or include it in your self assessment etc. There are also investment ISAs, where the money you put in will be invested for you. This is more risky as with any investment, it can go down as well as up, but over the long term it's typically a safe bet, and any gains you make from that are also tax-free. There are a range of investment ISAs, including 'safe' and 'high risk' options, as well as in specific markets, so you can choose which one appeals to you the most. Obviously the higher the risk, the more you stand to make in returns, but the more likely it is you might actually end up with less than you invested. The 'interest' is what you earn on the money you have in there, typically about 3% at the moment. Usually, even with a normal savings account, you would have to pay income tax on that interest. An ISA is tax free. You put in money you have already been taxed on, like a normal bank account, up to £20,000 a year. You can have multiple ISAs, but the limit of £20,000 a year is spread across all of them. You cannot carry allowance over to the next year, so you either save the full £20,000 each year, or miss out. Some providers will give you better rates than others, in exchange to longer withdrawal periods. There are plenty where you can take money in and out pretty quickly, without penalty or charge. Obviously the 'gains' are not huge at first - you're only saving the tax on your interest after all - but over time, it mounts up. They're intended as longer term saving pots.