Alright, so I'm probably going to start an ongoing blog series covering my experience with the Trials in Super Street Fighter IV. Before I jump into that, though, I need to provide a little foundational knowledge, and frame data is the perfect place to start. If all of this is too basic, though, by all means, skip down to the bottom for a link to the character tutorial you're looking for.
Bear in mind that these fundamentals, by and large, apply to many different video games, especially fighters. However, as I continue this blog, I'll start honing in more and more on SSFIV specifically.
As an aside, I just want to point out that I'm not trying to come off as some sort of fighting game know-it-all or even an amazing player. I'm pretty solid and I can do the trials... that's about it. I only wanted to do this blog series because some of the trials have outrageously obscure tricks you have to know to make them work. Others seem quite a bit harder than they already are. I've taken so much from the community in terms of SF knowledge that I just really want to give a bit back. That's it.
Feel free to copy this information anywhere you want to, and by all means, share it. Accreditation appreciated.
Frames
Any screenshot you've seen of any in-game footage is showing you a single frame of that game's animation. Any time you pause a game in the middle of the action, you're looking at a solitairy frame.
Think of a flip book. Each page in it is analagous to a "frame" of animation in a video game. When you flip through a flip book, you see a series of still images, one after another, at a fast rate, creating the illusion of animation.
That is analogous to how video games are animated, where each hypothetical flip book page equates to a frame. However, in the case of video games, you are seeing a much larger amount of those still images, and they are zipping by much more quickly than in a flip book - 60 frames every second.
So, why does this matter? For one, just like anything else you might want to devote some time and energy into, it's good to have a strong understanding of the fundamentals. But in the case of SSFIV specifically, many of the game's combos (especially the Trial combos) use 1-frame links.
Combos, Strings, Target Combos, and Links
Combos are sets of moves that can not be blocked or interrupted as long as two conditions are met: 1) the first move of the combo hits successfully, and 2) the person doing the combo executes the rest of the moves in the combo properly. Combos can consist of any combination of normal moves, special moves, Super moves, or Ultras. A common example from SSFIV would be Ryu's jump-in roundhouse, crouching fierce punch, hadoken. From the moment the jump-in RH lands, the rest of the combo is guaranteed to connect as long as whoever is doing it gets it right; the person getting hit has no way to stop it.
Strings, sometimes called chains, are simple, usually low-damage combinations of a single normal move that can be done by rapidly pressing the required buttons. A very common string would be three crouching jabs. These combos are relatively easy to do, and don't require much in the way of precise timing. As long as each successive move is performed within a certain amount of time - within a given number of frames - the string will connect as a successfull combo.
Target Combos are just like strings, except they involve more than one normal move. Ken's standing medium punch into hard punch is a target combo.
Links are similar to strings in that they consist only of normal moves, but differ in that they require more precise timing to execute. An example from SSFIV would be Ibuki's standing light punch into standing medium kick. If you try to do this combo by simply pressing light punch and quickly pressing (or mashing) medium kick, the combo will fail. To make it work, you have to press medium kick at the precise moment - a certain number of frames - after the light punch hits. One frame too soon, and the medium kick won't come out. One frame too late, and the medium kick gets blocked. This is what we refer to as a 1-frame link
Most of the difficult Trials in SSFIV combinations of strings and 1-frame links. What's more, the timing for links is not always the same. Standing light punch into standing medium kick with Ibuki, for example, requires a completely different timing from Adon's crouching light punch into crouching medium punch, and the only practical way of learning these differences is through trial-and-error.
In Summary
Remember that most of this information applies to every fighting game, but there are some differences. Certain games, like BlazBlue, for example, have a mechanic that allows combos to be interrupted. The series I'm writing is intended to explain SSFIV, though, so if you find information that appears to conflict with this, remember it might be a game-specific difference. That said, if I've just flat got something wrong, here, let me know and I'll make the adjustments.
Frame: One of several still images within animation, analagous to a page in a flip book; what you see when you pause the game mid-fight at any given moment. SSFIV animation runs at 60 frames-per-second.
Combos: Moves done in succession that are guaranteed to connect and cannot be interrupted as long as the first move hits and the person doing the combo does all the moves correctly.
Strings: Also referred to as chains, these are simple, usually one-button combos with very lax frame requirements that consist of only normal moves (e.g. three crouching light punches).
Links: Combinations of normal moves that require frame-specific timing to execute (e.g. crouching medium kick into crouching light kick with Balrog).
Target Combos: Like strings, but involve more than one normal move. (e.g. crouching light kick, crouching medium kick, standing medium punch into fierce punch with Dudley).
Character Trials:
Ibuki