To activate them you have to press the keys on your keyboard in the right order. Everything between two quotes is a cheat code.
Cheat codes:
"nbufo" Let's you fly by holding down space
"nbreflect" Activates Mirror mode
"nbfrog" Makes you jump higher
"nbman" Makes you jump normal
"nbgotta" Makes you run fast, activating this a second time makes you run normal
"nbwoohoo" Slow down Time
"nbponcho" Don't really know (changes something regarding lava)
"nbkfa" Give all weapons, keys and restore all stats
"nbkeys" Give all Keys
"nbullets" Infinite Ammo
"nbdeity" God mode
"nbff" Weapons fire faster
"nbregularfingers" Weapons fire at normal speed
"nbhot" Time only moves when you move
"nbspoder" Climb anything
"nbshooters" Give all Weapons
"nbdeathless" Restore all stats