In order to help you share your data with users but at the same time maintain some control of the data there are some special permission levels defined in the system. You view and change these permissions by choosing "User Permissions" from the main menu.
Any user you add to your account can view all layers of all maps on your account.
In order to change the content of a layer, a user must be an authorized editor of that layer. This permission level is required to do things like draw new features, change feature text, move feature geometry, delete features, or add/remove fields. Any number of users can be authorized as editors of a layer. You must be a Map Manager to set authorized editors for a layer.
Work orders layers are an exception to the layer editor control. Work orders manage their own permissions based on who the owner and assignee's are of the individual work orders. So it is not necessary to setup layer editors for this type of layer.
While the Layer Editor has authority to edit the content of a layer, only the map manager has authority to alter the organization of those layers within the map. You must have map manager permission to add a new layer, remove a layer, or permanently change the display settings for a layer. I say "permanently" because any general user can change the colors and other display settings for a layer but those changes are only seen on that user's screen during their current session. When the user closes and later re-opens their map they are returned to the default settings established by the map manager. Any number of users can be a map manager and it is common that some users may be both map manager and layer editor.
The Account Manger is the one user who has top level authority over the mapping system as it pertains to their agency. The account manager is the only one who can add and remove users from the account and the only one who can initially create new maps. You can have up to 3 account managers on an account.
See also Who Can See My Data