A wet vent is when a drain line serves as a vent for one or more fixtures. This can be either a vertical vent or a horizontal vent. Such as a bathroom lav that drains into the toilet vent (shares the same pipe)
Every fixture or trap requires a vent- wet or dry.
In your case, it sounds like you are moving a line that shares a vent with another fixture- so you need to add another vent to insure the altered work or the existing work is properly vented