Okay. What are splits? Well, splits are something that you have available to you when you're working on the same string in different ways.
A perfect example is if I'm raising the B string with my A pedal I'm raising it a whole step. If I'm looking to get just halfway there the best way to do that is to keep my foot on the A pedal and reach up for what we call the B lever. Which is the B lower and that's a vertical lever which means it's going across here not on either side of my leg. So, I just raise my knee up so you can hear that it's splitting the difference, hence the name split.
This is especially useful for making minor chords out of A and B position chords. If we're in the key of G on the tenth fret so then we have a minor chord on the same fret. If we want a G seventh chord we have the same relationship occurring with the sixth string which is affected by the B pedal. It raises it a half step. Now, the right knee going left lowers the sixth string a whole step.
So, once again, you're splitting the difference. You lower it a whole step, then you engage the pedal that raises it a half step. So, you've ended up lowering it only a half step to get the note you want. In this case you get a nice seventh chord by engaging the A and B and lowering the sixth.
So that's what splits are. It's basically the combination of two pedals that are working in opposite ways finding a happy medium that's yet another option for you.
This is not an option available to people who own push-pull pedal steel guitars. That technology did not permit splits, and basically whatever the first change you hit that was the one that won. If you added the other one that would countermand it or modify that you were out of luck. Nothing was going to happen.
But that's one of the advantages of all-pull guitars is that you do have splits and they can be extremely useful.