A family of Microsoft relational database management systems designed for ease of use.
A Trusted Location is a folder that you have indicated is to be trusted. This can be done in the Options settings of your Access application.
In order for your users to connect to the database, you must give Create/Read/Update/Destroy permissions on the folder.
Each user should have their own local copy of the frontend. The frontend can be installed anywhere you'd like on the user machine, but Documents is typically a good place. You'd have to set that as Trusted Location also.