Nexus is an information network started in YE 37 dedicated to making it easier for a private worker to find a contract to work in the vastness of space.
In essence Nexus is a job listing network. Clients from all over the sector can post job request to Nexus where all Nexus members can see it. A member decides to take the job and then does what's required by the client. After completing the job the member can either go directly to the client to report, or report at any of the Nexus affiliated locations.
From an OOC perspective this means players picking a mission from a job list and either getting a GM to run the mission for them, or running the mission themselves, but getting the GM's oversight to make sure things are going well.
Derek Wells used to make his living as a cargo runner, delivering any and everything he could. But in YE 36 he retired. Between the cargo hauls and stocks he made himself a decent fortune and could settle down with his family. Though he was satisfied with his life he wanted to give back to what had made him successful and founded Nexus in YE 37, so that private workers would not have to struggle as much as he did to find jobs.