This article goes into detail.
Here are some that I found:
The eosio.token contract. This contract enables you to create, issue,
transfer, and get information about tokens.
The msig contract enables and simplifies defining and managing
permission levels and performing multi-signature actions.
The eosio.system contract contract provides the actions for pretty
much all token-based operational behavior. Prior to installing the
system contract, actions are done independent of accounting. Once the
system contract is enabled, actions now have an economic element to
them. Resources (cpu, network, memory) must be paid for. Likewise, new
accounts must be paid for. The system contract enables tokens to be
staked and unstaked, resources to be purchased, potential producers to
be registered and subsequently voted on, producer rewards to be
claimed, privileges and limits to be set, and more.