Ok I'll use the Smash Lab Terms List
Turnaround B - Character changes the direction they're facing while momentum remains the same. Press back right before pressing B.
B-reversal - Character changes the direction they're facing AND momentum changes. Press back right after pressing B.
Wavebounce - Character changes momentum while facing the same direction. Press back before pressing B, then press the opposite direction after pressing B.
So, to give an example, pretend you're a Lucario running to the right. You jump right while facing right, and you're going to do all 3 of these to your ASC. You rise, initiate ASC at the peak of your jump, and then you fall while charging your AS.
Turnaround B - Press left (I find flicking the analog is the easiest way to do this) and then press B.
While rising, Lucario is moving right and facing right. While falling, Lucario is moving right and facing left.
B reversal - Press B, then press left immediately after.
While rising, Lucario is moving right and facing right. While falling, Lucario is moving left and facing left.
Wavebounce - Press left, press B immediately after, then press right immediately after. (Double-flick makes this easiest imo). Pretty much, this is a turnaround B-reversal.
While rising, Lucario is moving right and facing right. While falling, Lucario is moving left and facing right.
The inputs I provided apply to all upBs, downBs and neutral Bs, with a few exceptions.
Obviously for sideBs, there is no turnaround-B; you can just press left+B (at the same time) and you'll face left and fall right. A sideB to the left...idk how else to put it XD
And, by extension,
there is no wavebounce for sideBs; you just sideB to the left and then press right.
I've wanted to make a general video about these for a while but I don't have a capture card and I'm poor.
Edit: Missed a question. There's a platform cancel dropthrough where basically you platform cancel, and you buffer a dropthrough immediately.
It looks like
this, he did it twice.
If you're confused (you might be cause it's pretty fast), what exactly he did was
Jump-->PCDT(platform cancel dropthrough)-->jump-->PCDT-->falling uair.
Since momentarily, you land on the platform, you get your 2nd jump (or multiple jumps) back, it can be kinda useful. eg ZSS is offstage and has already used her downB, she PCDTs the SV platform to get it back; now she has her 2nd jump AND her downB.
Anyway, I'm rambling. The input for it is shield+smash down on analog (when I say smash, I mean press down quickly. Like doing a smash attack, but instead of pressing A, you press shield). When I found out about it I practiced it for like 2 hours straight and was only getting it like...40% of the time at most. Then I realized that since I have Y set to special, I don't use the B button for anything, so I tried setting it to shield to see if it would make PCDTing more easy...and it did.