If a creature is falling more than 10’, they take damage of 1d6 for every 10’ fallen. (If a character is playing a particularly agile character like a monk, the DM might allow them to make a DEX save if falling 10-30’ – up to the DM)
Any character that takes damage from falling, automatically falls prone upon landing.
The max damage a character can take is 20d6. Which means that the damage from falling 200’ is the same as falling 2000’. It is that whole terminal velocity thing – at some point you wont be going faster when you hit.
This damage is the same for monster, or player. So it can be a useful tactic to inflict damage.
Pro tip – monsters immune to bludgeoning damage, are not immune to falling damage.
Pro Pro DM recommendation – if a creature or player falls from a significant height, I would make them prone AND stunned for 1d4 rounds.