What does ventilate mean?

Bleed: A hydraulic brake system is opened so that air can escape. This has to be done because air can be compressed. Oil, on the other hand, not. Would be air in the hydraulics system. Then it may be that the brakes no longer work properly.

Bleed:
You open a hydraulic brake system so that air can escape. This has to be done because air can be compressed. Oil, on the other hand, not. Would be air in the hydraulics system. Then it may be that the brakes no longer work properly.

Relevant contributions:
Spring check bike, V-Break set