An ISA (individual savings account) is a tax efficient savings or investment account available to UK residents. You can read the official info here.
There are cash ISAs and stocks and shares ISAs. With a stocks and shares ISA, you can make your own investments in stocks, ETFs, bonds and other investments.
Any returns on investments you make, including income from dividends, through the ISA will be tax free. In contrast, investments not held in an ISA may incur capital gains or income tax.
You can have as many ISAs as you want, but you can only open or contribute to one stocks and shares ISA each year.
You can contribute up to £20,000 per tax year across the various types of ISA (for example, £10,000 into a cash ISA and £10,000 into a Stocks and Shares ISA), but you can only pay into one of each type of ISA per tax year.
For example, if you pay £100 into a Stocks and Shares ISA with Provider X, you cannot then contribute to a Stocks and Shares ISA with Provider Y in the same tax year. But you would be able to contribute to a cash ISA.
Freetrade allows you to open a Stocks and Shares ISA on both basic and Alpha accounts.