When you fall a distance of 10 feet or more, you take damage from the fall. This damage can be negated by the Slow Fall boon, but if you don’t have that then you’ll need to use Break Fall to try to avoid hurting yourself too badly.
The amount of damage you take from a fall is equal to 1d6 per 10 feet you fall. The Cat Fall feat can reduce the effective distance you fall for the purpose of calculating how many dice of damage.
When you would take fall damage and are not Unconscious, Stunned 4+, Slowed 4+, or Restrained, you can attempt to absorb your momentum to avoid hurting yourself too badly. Make an Acrobatics check against a DC equal to 10 plus the distance you fell in feet divided by 5, rounded down.
If you are Unconscious, Stunned 4+, Slowed 4+, or Restrained, or otherwise unable or choose not to make this check, you are affected as if you had Critically Failed this check.
You can fall a maximum of 600 feet in a single round (effectively terminal velocity). Note that if you are falling more than 50 feet, the GM could reasonably say that you don’t hit the ground until an entire round has passed, possibly allowing your allies to rescue you before you go splat. This is up to the GM’s discretion, however.