A bar freeze in Pokémon Red/Blue, caused by stepping into the 'grass' right of Pallet Town.
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 softlock, or lock-up, simply refers to when the player is stuck in a loop, either with the controls not responding or, for example, being infinitely forced to do an action. Music may still be playing.
This is a kind of game freeze often encountered when using a walk through walls glitch. It fills the screen up with mostly full vertical bars, some interrupted with seemingly random letters and numbers.
When this freeze happens, many memory addresses are replaced with '00 39'. (More information can be found here)
Example: Stepping into the first column of 'grass' tiles east of Pallet Town.
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 also referred to as a 'BSoD' (Black Screen of Death) in the Hall of Origin community.
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 dokokashira door glitch in Pokémon Red/Green to enter a location which does not exist.