If you’re interested in using a rowing machine for focused training — whether for outdoor rowing, an indoor competition, or as part of a larger fitness program — you’ll want air resistance. If you’re drawn to rowers for the enjoyability (alongside the full-body, cardio-plus-strength training efficacy) of a rowing workout, consider a machine with water resistance.
On a rowing machine, you don’t want to be wearing clothes that are too baggy as the fabric can get caught between the seat and the beam it slides on.  It’s not a disaster if that happens, but it can get annoying if your shorts keep getting caught there while you’re trying to get a serious workout.   It’s better to wear shorter, tighter-fitting shorts (nothing ridiculous), but just enough to ensure it doesn’t the material doesn’t hang down.

In sweep or sweep-oar rowing, each rower has one oar, held with both hands. This is generally done in pairs, fours, and eights. In some regions of the world, each rower in a sweep boat is referred to either as port or starboard, depending on which side of the boat the rower's oar extends to. In other regions, the port side is referred to as stroke side, and the starboard side as bow side; this applies even if the stroke oarsman is rowing on bow side and/or the bow oarsman on stroke side.