Watch enough NFL practices and you'll start to recognize the most common drills. There's "9-on-7," which usually emphasizes the run; "7-on-7" periods are all about the pass; "indies" are all about technique at individual positions; "special cat" can refer to work on specific game situations, such as a two-minute drill.
There are some common pairings of drills, too. Since receivers and cornerbacks don't take part in 9-on-7, it makes sense to take them to an adjacent field for 1-on-1 reps at the same time. The offensive and defensive lines don't join in on 7-on-7, so it's a good time for them to face each other in 1-on-1 pass-rush snaps.