In Manage My Vessel Trips are a way to log where the vessel has been, as well as where the vessel intends to travel to.
When a trip is created you will be able to link crewmembers and guests to a trip and also link forms to it aswell. This will have been set up by your management company.
Once a trip has been created and completed a user role can then close the trip, preventing it from being modified again and locking all the information that has been entered for that trip. This is particularly useful to keep a record of the vessels movements.