Most ICO tokens are issued on Ethereum blockchain. It means that people who want to participate in ICO need to have Ethereum and its wallet. However, not all digital wallets support Ethereum powered ICO tokens. For example, to participate in Fast Invest ICO, you need to set up an Ethereum ERC20 compatible wallet where you and only you hold its private keys. You probably know that ICO is about sending and receiving coins. Your private keys are necessary for correct interaction with smart contracts to transfer and receive tokens.