General movement is movement within a class of movements. You could consider a bilateral squat or "deep knee bend" a general movement. You could could consider hip extension with lumbar control and general movement. Basically any basic fundamental movement that tends to be a part of other more specific exercises or lifts (in our case). A lunge, for instance could count. Remember this has to do with varied versus blocked practice, as I explained in the overhead squat book.
Remember from the overhead squat book one of the main points I made was the difference between initial improvement and learning overall. Let's say you're a beginner and I give you varied practice rather than blocked practice. We're keeping this discussion to one class of movements by the way. So let's say I give you lunges, posterior chain work, and overhead squats. You're practicing all of that while the other guys are ONLY doing overhead squats.
They seem to "learn" the overhead squat faster than you. Their initial improvement is on the OH squat is greater than yours. However, you will, at some point in the near future surpass these other guys for many reasons. Not the least of which is you will simply learn faster, have higher transfer, etc. This will be true even if you go to using blocked practice.
Take that a bit further and suppose that you have this varied practice for a while while the other guys are just doing the overhead squat. Now let's say we introduce a new lift to you and the other guys, and we stick to blocked practice. You will tend to learn and improve on the new lift faster than the guys who started with non-varied practice. The point, then of "learning" versus "teaching" is that learning begets better learning and has a long term benefit down the road and throughout the lifting career.
Motor learning schema and "perceptual schema" is not exactly the same thing. When you do a deadlift, part of the motor "schema" would be hip extension. This is automatic. A mental schema is more a cognitive construct. Not a lot of people have ever talked about it in terms of weight lifting or athletics in general. Whereas the individual movements or movement patterns that make up a larger more complex movement are part of the motor schema, the mental schema is your "mental representation" of that movement.
Again, in the OH squat book I explained this in terms of showing someone a squat. When we see a movement we see what our "perceptual schema" of the movement colors it as. This is related to my problem with people looking at images to learn lifts. So perceptual schema has to do with the process of teaching rather than the actual motor learning although of course this is interrelated.