Using Stealth Mode Lara can move around an area without being immediately discovered.
The Angle of Darkness
It has to be activated manually by pressing the Stealth Button (Return on PC and L2 on the PS2). Lara will change to Stealth Mode and sneak around in a slightly crouched position.
Stealth Mode can also be used while crawling. Press the Stealth button while crawling and Lara will lie down flat on the ground. She can use this bellycrawl to get underneath laser beams e.g. in Von Croy's Apartment.
The Stealth Mode makes a reappearance in the Reboot Games (Tomb Raider (2013), Rise of the Tomb Raider). Here Lara will automatically switch to Stealth Mode whenever Enemies or dangerous animals are near. She can still be seen by enemies while in stealth mode unless she hides herself in bushes or behind barriers.
Stealth Mode can be used to sneak up on Enemies from behind. If Lara gets close enough the player can press Y to use either the Bow to strangle or the Combat Knife - if available - to kill the enemy silently. If Lara is very careful she can clean out whole areas using this tactics; if she succeeds she will get an additional XP bonus for not being seen.