What is realism mode on L4D2?

Answer 1

it is basicly a realistic version of the game, you can get lost easy and there is NO HUD.
Plus the Zombies wont die until there head i severed off.you need to work as a team and stick together

Answer 2

Realism in Left 4 Dead 2 is a game play mode, sort of like campaign but :

1. Outlines around the Players, Weapons, Items, Pinned Survivors, Ect are REMOVED.

2. Common Infected can take more body shots than normal, Head shots are 1 hit kills.

3. Dead players will stay dead unless revived with a defibrillator or if you reach the safe room.

4. Witches Instant Kill on any difficulty except Easy.

5. Witches are harder to "Cr0wn".

6. There is a significantly increase in witch appearances.