What is EOS account name?

1. what is an EOS account?

Instead of having only public and private key like other blockchain, EOS user must have an account name. An EOS account is a readable name that is stored in the EOS blockchain and connected to your keys. An EOS account is required for performing actions on the EOS platform, such as sending/receiving tokens

2. What's the rule for it?

It must be exactly 12 characters long and consist of lower case characters and digits up until 5.