Frames.

Hey hey, Marcus here. If you have picked up Tekken just recently/ been playing for quite a while now or am about to pick up Tekken, you would most probably have read the Tekken Zaibatsu forums for more info regarding your character... Right?
If you have never heard of Tekken Zaibatsu before, I seriously recommend you to go check it out, its probably the most info intensive forum on Tekken ever, so its definitely a good read before venturing out into a higher level of Tekken play. Click here for Tekken Zaibatsu forum.

If this is your first time hearing about frames, you are in luck, because personally, I feel than 50% of the game is governed by frames, they are so important that I can't stress just how much of it you need to know, in fact, i believe frames are what separates a pro from a regular person that i believe a lot of players in our scene has been playing for quite a while now but never realizing this wondrous thing.
So buckle up and listen (or read) good.

Frames in its true essence is just simple math, math that governs the game. Every move of your each character has their set frames, frames when the move is blocked, frames when the move hits, frames when the move gets a CH, and the start up frames or the iframes (instant frames) of a move.

Have you ever wondered why you seem to never be able to damage the pros at all while you eat all of their moves? That's because of frames.
There are two parts to frames, a positive frame and the negative frame. Negative frames and positive frames affect both you and your opponent's iframes for the next move. Moves that gives you negative frames will add iframes into your next move causing it to come out slower while it adds iframes to your opponent's next move causing it come come out faster and vice versa for positive frames.
An example would be imagine you do a move that gives you +4 on block/hit/ch and you plan to do an i10frame move next, due to the +4 advantage you have, your move will be 10-4= i6frames!
While if you did a move that gives -4 on block/hit/ch and you plan to do a i10frame move next, your move will be 10+4= i14frames. So if you have experienced why your moves lose out to your opponent's one, this is why.

Now, I'm going to introduce the term punish and safe. Punish refers to using a certain move with a certain iframe right after your opponent's move and it will hit them. Usually, the fastest punishers would be a i10frame move. Now you know that some moves have -frames on hit/block/ch, but some has such a high -frame that it allows a move from the opponent to hit. An example would be you did a move which gives a -13 on block, this means that your opponent's i13 and below moves will definitely damage you if they execute it immediately. This is called punish.
Safe moves are moves that ensures you to be able to block your opponent's move as long as you hold back/block immediately after you finish the move. Safe moves are moves that give +/-0 to -9 frames on block. Any move that gives -10 and above on block are considered punishable. However, do not that although some moves gives high -frames on block, but due to their push backs, they are safe because the opponent's punish can't hit.

Now this is a really basic overview on frames and it is something that you have to read up on and gain through loads of playing and experience. But for now, I strongly recommend going to Tekken Zaibatsu and reading up on their forums as they provide really great information on all of the Tekken casts, and as well as reading up on here as the people from Tekkentrack.com did a really great job in compiling and translating the frame data for the cast.