Taken from the Street Fighter Anniversary Edition guide that MrWizard helped make:
Poking
Advanced gameplay involves several tactics to win. Most players will use a barrage of normal moves instead of just doing special moves. Using safe mid-range or long range attacks is known as “poking.” Many special moves take much longer to recover than normal moves. As such, they are more risky against experienced players who know the proper counter-attacks for them. Since poking is rather easy and safe to do, it is more common than a lot of other techniques.
Example: Vega’s long-range crouching LP enables him to continuously barrage any opponent with annoying pokes. This makes it very difficult for an opponent to get close to Vega or perform slower attacks, such as throwing projectiles.
Footsies
It’s difficult to mount an effective long-range zoning gameplan against characters who have a strong attack range. In such cases, it becomes necessary to play “footsies.” The term footsies is basically a subset of zoning that is focused primarily on close-range normals, where the most common goals are to knock the opponent down and set up cross-up opportunities.
Staying within close proximity reduces the advantages present in an opponent’s long-range normals. It creates a sense of anxiety and pressure for an opponent, who now risks damage to a much greater degree than facing your character at a great distance. Although such close proximity places your character in danger as well, it’s a strategic sacrifice that is necessary to maximize your character’s close-range arsenal. If an opponent attempts a slow, long-range attack to push you away and force you to block, attempt a cross-up to force the opponent into a difficult guessing game. If an opponent attempts a quick short-range attack instead, stay just outside of the attack’s range and use a crouching HK to counter attack when it whiffs, or fails to make contact. Knocking down an opponent in this way creates an advantage for the offensive player by allowing for a guaranteed cross-up or a tick-throw attempt.
Example:
Since Guile’s normals have a greater range than Ryu’s, it’s important for Ryu to stay close to Guile and play footsies. If Guile tries to push Ryu away with his crouching MK, Ryu should walk back to force it to whiff and punish it using his crouching HK sweep. If Guile tries to throw a Sonic Boom, Ryu can jump over it and go for a cross-up attack. If Guile becomes reluctant to attack, Ryu can simply inch forward and throw him. This entirely close-range guessing game is known as footsies.
Footsies isn’t confided to just sweeping. 3S Chun Li is a perfect example of a character that relies on superior footsies. She uses far s.hp and c.mk as methods of punishing attacks that she’s baited. The term footsies is in reference to the dancing back and forth outside of range.
On a Tekken note, poking is done close-range as well as mid.