An account module simply allows users in the system to log in and perform tasks like setting their preferences or configuring the details of their account. Users may be configured into groups, companies or both. Permissions between users are often used to give more or less actions to different types of users.
More complex systems often allow hierarchical configurations, with groups being split up between departments and countries. Integration with LDAP or Active Directory servers or the use of Single Sign-On means users may log in with their existing credentials.