Fullbright
Lights up dark areas so you can see without torches.
Fullbright only changes how the world is lit on your screen. Your gamma option and your real potion effects are left alone, so turning it off puts everything back exactly as it was.
Mode
How the world is brightened.
- GAMMA: pushes the brightness past the vanilla slider's limit. Dim areas become bright, but spots with no light at all stay dark
- NIGHT_VISION: lights the world the way the Night Vision effect does, without the effect showing up on you
- FULL: lights every block evenly at full brightness, including caves with no light at all
Gamma
Only visible in GAMMA mode. How far past the vanilla brightness slider to go. 1 matches
the slider at Bright, and higher values brighten dim areas further.