From Glitch City Laboratories
A game freeze refers to the instance of where a game's controls lock up disallowing the player to play the game normally. Through different glitches, different varieties of game freezes have been found. Sometimes music may be frozen on the current note but sometimes the music will stop completely. On rare occassions, the music will still be playing.
Types of game freezes
A lockup simply refers to when no controls have any effect. Music may still be playing.
Example: When the player attempts the bp:Generation I variation of Wild appeared!.
This is a kind of game freeze often encountered when using the Cooltrainer move. It fills the screen up with mostly full vertical bars, some interrupted with seemingly random letters and numbers.
Example: Frequently when the player uses the Cooltrainer move.
Black screen freeze
When the game freezes this way, it will switch to a black screen. Music often freezes on the note it was playing when this freeze happens.
Example: Can appear when the player uses returns to the overworld after using the Explorer Kit in an invalid area through accessing a 'void' in Generation IV. This phenomenon is often referred to as a 'BSoD' (Black Screen of Death) on the Hall of Origin website.
White screen freeze
When the game freezes this way, it will switch to a white screen. Music often stops completely when this freeze happens.
Example: When the player uses the Doko kashira door glitch in Pokémon Red/Green to enter a location which does not exist.