There are two types of employee / user:
Admin users have access to all areas of your account. You can have as many account owners as you desired.
Standard users can have specific permissions set. To set these, go to the "Employees" tab from the "Set Up" page and click on the Employee you want to edit his/her user role. There will then be a pop up on the right hand side of the page:
If you scroll down, (under Biography option) you can select "Standard User" from the "User Role" drop down then you will see the following permissions that can be individually granted to the user optionally: