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. Additionally, Crush Counter hits build the character's V-Meter, which can put them one step closer to activating their V-Trigger or perform their V-Reversal.
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. Generally, every characters' sweep is a default Crush Counter move. Some Special Attacks, such as Laura's V-Skill have also Crush Counter properties.
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. However, it can be Crush Countered during the startup frames.
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.
Crush Counters constantly keep getting updated with balance changes. One of the latest is the amount of points they add to the Damage Scaling chart. Players should keep this in mind to maximize punishes that involve said tactic. Gill is the only character in SFV who is not equipped with a Crush Counter move.