An EOS account has keys associated with it. Each key has a certain permission.
Example of key permissions and can be generated to buy/sell RAM but not to transfer coins or tokens. This means that if you give the private key to someone else they would only be able to buy/sell RAM but not transfer any of your coins or tokens.
The most common keys generated for EOS accounts are Owner and Active Keys
Owner Key: The Owner permission is the "root access" to your EOS account and symbolises ownership of the account. Only a few transactions requires this authority. Access to the private key for the Owner permission will allow you do perform any function on your account. It is generally suggested that you keep your Owner Key in cold storage and not shared with anyone. If you Owner Key is exposed then your account may be compromised.
Active Key: Active permission is more restricted. It is used for transferring funds, voting for block producers and making other high-level account changes
For more information on account permissions and set up check our the resources here: