lol @ first statement...
usually when you hit a button, your character does whatever action is associated with it... ie hitting your jab button makes your character do a jab... when you're in the middle of a move, you can't do anything, so if you're in the middle of a nair, and you hit jab, jump, or anything, nothing will happen...
buffering is when you hit another input near the end of a move, the game "buffers" this movement and performs the action the very first frame possible... this is basically a technique for getting moves out as quickly as possible, and makes it less twitch-gaming (by giving you a longer input time for the best results)
usually when you hit a button, your character does whatever action is associated with it... ie hitting your jab button makes your character do a jab... when you're in the middle of a move, you can't do anything, so if you're in the middle of a nair, and you hit jab, jump, or anything, nothing will happen...
buffering is when you hit another input near the end of a move, the game "buffers" this movement and performs the action the very first frame possible... this is basically a technique for getting moves out as quickly as possible, and makes it less twitch-gaming (by giving you a longer input time for the best results)