The company module defines the concepts of company and employee and extend the user model.
The company model extends the party model and add several fields: the currency, the list of employees and header and footer texts for reports. There is also a parent company field which allow to setup companies in a tree structure. The company model represent the actual organisation the users of Tryton are members of.
The employee model extend the party model with a company field. The employee model represent the actual employees of the companies defined in Tryton. An employee can be optionally linked to a user trough the user form.
Are added to the user model: a main company, a company and an employee field. The company field defines the current company of the user, this current company will influence the data this user see in Tryton: most of the records that are linked to a company will only be available for users in this very company. The main company define which current company a user can choose: either the main company itself or one of the children companies.