What is the difference between giving someone a "trusted role" and putting someone in default group?

[Fahad Akhtar]

When I invite a user through user management, I can choose there role for them. Either basic, trusted, or site administrator. When I put them in trusted they are put into the jira-servicedesk users group automatically and use up a license. I want to know what the difference is. Could I do either or and it means the same thing or are these two different things? Same goes for basic, could I give them a basic role or could I make give them the project role of service desk customer? If I decide to list a group under product access for JIRA in user management do the people in those groups use up a license? I feel like in JIRA, you can do a lot of different things but get the same result like what I have stated above, is this true. Thank you. 

[Mikael Sandberg]

If you select trusted, the user will get access to all your applications and they also becomes admins of those applications. If you give them basic you have to select which applications they get access to.