Blocking is used to block an incoming attack, it also ties into both of the following:
- Posture - (the bar leading up to a guard break, if your posture gets full, you can be guard broken)
- Block Breaks/Guard Breaks (a guard break is when your block gets broken and leaves you stunned for several seconds)
Do not treat block as a permanent shield. Critical attacks bypass it; use dodge or parry to avoid relying on an already full posture bar.