As an account owner (or a user with user management rights), you have the possibility to invite users to three different levels and with different rights (view/edit/user management) at that level.
Account level:
If you are invited/invite to an account, all websites and projects in that account are also shared with the same right level as the account.
Website level
If you are invited to a website you get access to all projects on that website.
Project level
If you are invited to a project you only get access to that project.
