A Stocks and Shares ISA is a type of tax-efficient savings account available in the UK that allows individuals to invest in a range of assets, including stocks, bonds, and funds. The money you invest can grow free from income tax and capital gains tax, making it an attractive option for long-term investors. You can contribute up to a certain limit each tax year, which is set by the government. Any returns you make within the ISA are not subject to tax, allowing your investments to potentially grow more quickly compared to a standard savings account.