This game mechanic isn't founded by anyone, as it's obvious to be seen. This replaces edgehogging by pushing the opponent back, whereas edgehogging would simply not allow the opponent to grab the edge at all. Edge stealing also gives the opponent lag during their 'pushed back' animation (they can't input anything out of it for a period of time).
Edgestealing is done by perfectly timing grabbing the edge (whether you be off stage or on stage) as soon as your opponent grabs the ledge. This, once again, pushes the opponent back into a 'pushed back' lag.
Here is where it gets just a
little tricky. As soon as you edgesteal (refer to above), you can attack your opponent by during their pushed back lag (yep, that's what I'll continue calling it since I can't think of calling it anything else). But the attack must have hitboxes which can actually hit your opponent, such as a few back aerials or specials. Out of this, you can actually KILL or even follow up with a multiple hit combo (this is quite possible, but gaining edge steals are quite tricky as you need timing).
Here is an example at 0:59 - 1:11 stolen from
Ganon boards (they seem to be the only board taking competitiveness very seriously, no really go and read their posts and compare it to the other boards). Basically Gungnir (the Ganon player) times his edge steal and follows up with a back aerial! Can this be done with a few suicide moves as well? Koopas claw? Ganoncide? Maybe, who knows. Needs testing.
Another brilliant example from the
same video at 3:40 - 3:51. Ganon gets a TRUE combo kill at 77%! The strong the attacks possible after an edge steal the better the move can be, but, as I said above, you CAN get other moves out of it just maybe for some quick damage, or maybe a double suicide, or maybe multiple hits leading to confusion.