Tekken runs at 60 frames per second, the fastest attack in the game with the exception of something like Yoshimitsu's flash is a standard jab at 10 frames. Quick mids average around 15 frames, slower mids averae around 20 frames and lows average around 17 frames in speed.
When a move is blocked, the block stuns of various attacks are different and can give you either an advantage on block or a disadvantage, same with connecting an attack. Moves are commonly disadvantaged on block and advantaged on hit, though with all the moves and move properties in the game, there are multiple exceptions.
If a move happens to give you +1 advantage through block or hit, and the very next thing you do as you recover is a jab, while the opponent also jabs as they recover; your jab will beat theirs by one frame, as their jab effectively took 11 frames to come out compared to yours. If you'd delayed your jab by 3 frames before you threw it, your advantage is lost and their immediate jab will beat yours.
Lets say you land a poke that gives you +6 on hit. Since the fastest attack they have is 10 frames and they have to wait until 6 frames after you to attack; it means that the fastest move they can make to counter you is 16 frames, so any attack you have tht is 15 frame speed or faster is too fast for them to interupt and will beat them out if they try to.
You you were only at +1 and they expected you to use your frame advantage to force a jab, they could duck the jab and punish from crouching, and you would have to risk the fast mid to beat them ducking. If you'd done that at +1, they could have jabbed out your mid, but at +6 you can do either with security and still beat them if they try anything.
If you have a move the has a juggle property on counter hit, or CH; you can calculate how to beat out which attacks and which is the best time to use the counter hitting move. If the move is 13 frames and you do it at the same time that an opponent attacks with a move that is 14 frames or slower, then you will CH their attack and get a juggle; just the same as if you used this move to beat a jab of theirswhile you were at +4.
Because jabs are 10 frames, an attack that has a disadvantage of -10 or more when blocked can be jabbed by your opponent before you can block. That means if you use it recklessly, they will keep using jabs to punish you each time. If the move has -15 on block and the opponent has a 15 frame move that launches, they can get a big juggle when they block if they punish correctly, so you have to be extra careful with the risk of moves that can be launched and can manage your risk accordingly. Moves that are -9 or less cannot be punished with jabs of course.
Similarly, moves that give +10 advantage or more can give you free jabs, but most commonly is the exception of 'false' frame advantage. When +10 allows jabs without them blocking, it is considered 'true' frame advantage, but most often with a move like a running attack that gives you +17 when blocked; they can't move or attack until after 17 frames, but they can block right away, even with jabs. What you can do with false advantage is use the fact that they cannot interupt anything you do by enforcing a mixup that makes them guess between blocking mids or lows that you might do.
Understanding you characters frame database allows you to use the mathematics to calculate when you use which moves and how to set up situations where certain moves are best, while you can also decide which punishable moves are worth the risk, and which moves are not worth the risk. Knowing frame data of opponents characters also means you understand exactly how to punish or play around their moves and which of your moves will punish their unsafe moves most effectively.
A lot more easy than trying to work it all out for yourself.