The benefits of web 3.0, a decentralized internet, is the same as the benefits of decentralization in general - less censorship, less middleman fees, more autonomy, etc.
A token is a fungible (interchangeable) or non-fungible (unique) asset that is used to represent a currency or other valuable, but is not the currency or valuable itself. In the blockchain space, tokens can be created on various smart contract platforms.
A token can be created on the Etherium smart contract platform using the ERC (Etherium Request for Comment) format - commonly ERC20 (fungible), ERC721 (non-fungible) or ERC1155 (for a contract that can do fungible, non-fungible or semi-fungible simultaneously).