Glass surfing is when a fish repeatedly swims up and down the front glass; it is a stress signal, often from an uncycled tank, wrong parameters, boredom, or seeing its own reflection.
Occasional exploring is fine, but persistent frantic pacing is worth investigating. The first check is always the water — test for ammonia and nitrite before assuming a behavioural cause.
In new tanks it often eases as the tank matures and the fish settles; in bettas it can be a reaction to a reflection or too-strong flow.