Street Fighter V implements a normal priority system similar to the one found in the Street Fighter III series. If active at the same time, medium strength attacks take priority over light attacks. This is unlike other games where light attacks beat medium attacks if they connect first. Likewise heavy attacks will ignore medium and light attacks.
Certain attacks, when landed as a counter hit in the aforementioned fashion will send opponents reeling back and put them in a state functionally similar to crumpling caused by Focus Attacks in Street Fighter IV series. In this state, the opponent is defenseless and the attacker can extend combos or do combos that aren't otherwise possible.
A counter hit on special moves using Crush Counter causing normals will also cause a Crush Counter state. A Crush Counter can occur against airborne opponents as well. Each character generally has two Crush Counters: one with a punch and the other with a kick. Some Special Attacks, such as Laura's V-Skill have Crush Counter properties as well.
Certain (non-EX) anti-air attacks like the Shoryuken or Cannon Spike can be punished by Crush Counter causing normals during their recovery animations, if they are blocked or whiff. The criteria for a move to be punishable this way is that it should have certain amount of invincible frames; Charlie's Sonic Scythe, for example, cannot be Crush Countered on recovery.
Crush Counters add another dimension to the neutral game. Players are encouraged to poke frequently and play 'footsies' in the hope of landing a Crush Counter, which can lead to some of the heaviest damage possible for any character. Crush Counters can also be used to visually 'hit-confirm' into Critical Arts.