This is a sign of exhalation.
Whales are mammals that breathe using lungs and must rise to the surface to inhale. The blowhole in cetaceans is typically located on the very top of the head.
This opening is equipped with a valve that seals tightly when submerged and opens when surfacing.
When a whale expels air from its lungs, this process is accompanied by a loud noise, and above the animal's head, one can see a "fountain" consisting of exhaled air and water vapor.
