If others will be managing your campaigns with you, we recommend adding them to your account as an additional user rather than sharing a login. This minimizes the need to share passwords by email (don't do it!!) and also allows for better event logging, which can be useful in case a change is made that you did not authorize.
Administrators have the same access as the main account holder, including the ability to manage billing and additional users on the account.
Adding a General User allows you to have greater control over access to specific profiles and to billing, as needed. When provided with full access, a General User can perform all the functions that an Administrator can, except for managing additional users on account.