Explain a Video Game Mechanic You Keep Getting Wrong

You have died to the same move eight times and the tutorial explained it once, badly. This breaks down what the mechanic actually does, names the mistake beginners usually make, and gives you one simple way to practise until it clicks.

Explain this game mechanic to me like I am new to it, because I keep getting it wrong in [game name]:

Mechanic: [describe the mechanic you do not understand, e.g. the parry timing, the crafting system, a specific ability combo]

Tell me plainly what it actually does, the most common mistake beginners make with it, and one simple way to practise getting it right.