Cut together two shots of the same subject from nearly the same angle, with time removed between them, and the subject appears to jump. Classical continuity editing treats this as an error to be avoided, traditionally by changing angle at least thirty degrees or changing shot size.
Godard made it a technique rather than a mistake in Breathless, where the jump cuts announce the film's own construction and give it a restless, modern energy. The device carried a specific art-cinema meaning for decades afterward.
Then the internet made it the default. Nearly every talking-head video on YouTube is built from jump cuts, because removing pauses and stumbles is the fastest route to a tight edit and viewers have been thoroughly acclimatised. The remaining craft question is whether the discontinuity is doing something — conveying compressed time or nervous energy — or is simply where the mistakes were cut out.