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Since any arbitrary code may be ran on Ethereum, contracts that create tokens of all types are possible. Bitcoin in its entirety could be a contract on Ethereum as a token, in fact Wrapped Bitcoin is a ERC-20 contract and is funded by BTC sent to a contract address allowing Bitcoin to be used in the wider decentralized finance, or DeFi, ecosystem! This is made possible in-part by Ethereum's ERC-20 standard. The ERC-20 (Ethereum Request for Comment #20) introduces a standard for fungible tokens which have a property that makes each token exactly the same (in type and value) as another token of the same contract. For example, an ERC-20 Token acts just like ETH, meaning that 1 token is and will always be equal to all the other tokens of the same type.
ERC-20 tokens are commonly referred as just tokens.
Some common examples of ERC-20 tokens are shown here in order of their total market share (Nov 2022):
Tokens on Ethereum or any of it's Layer-2s have a contract address associated with the ERC-20 token that is unique to the contract that created the token. For example the DAI stablecoin contract has this contract address: 0x6B175474E89094C44Da98b954EedeAC495271d0F. DAI stablecoin always has this exact contract address on mainnet.