How does crouching work?

[Qdude]

When you press C, normally my character goes down to a full stealth crouch. But other times, he goes down to a sort of sneak walk position and he also talks less quiet then he should in this position. What causes this?

[lucebuce]

When you press C, you enter "Stealth mode". When you do that, certain actions just become stealthier. You walk a bit slower, you run while crouched, you whisper instead of shouting when you try to speak.

The thing you mentioned of crouching down much lower happens when you're next to a fence or a big object like a car or a wall. Basically anything you can lean on or crouch underneath. You are least visible when you're crouching like that and it's a good way to do stuff like break line of sight.