How EOS accounts work
An account is a human-readable name that is stored on the blockchain. It can be owned by an individual or group of individuals depending on permissions configuration. An account is required to transfer or otherwise push a transaction to the blockchain. — EOSIO Wiki
Every EOS account is 12 characters long and contains the characters a-z and 1–5. An EOS account consists of 2 keys, the active key and the owner key. The active key can be used to transfer funds, vote for block producers, buying ram, etc. The owner key shows ownership of the account and is needed to make any changes to the ownership the account. This key is best kept (safely) offline, as it is not needed to do most things on the EOS network.