If you want to give certain people in your organization access to a limited set of your apps you can use teams.
Every user in your organization is a member of the "Everyone" team. You cannot remove anybody from the Everyone team. Besides the Everyone team you can create as many teams with specific members as you like. You can specify which apps a team has access to.
Once you create a team you can edit its name, app and members. Select a member and add him/her to the team, or remove a member from the team.
Select an app and give the team access to this app, or remove access to the app.