Pain tolerance is genuinely different for everyone so both things you've read are probably true for different people. The most common description is that it feels like a quick snap or a flick against the skin, and it's followed by a brief warm sensation. Most modern laser systems used at professional clinics come with integrated cooling mechanisms — either a cooling tip, a cold air device or a built-in cryogen spray — which significantly reduces the discomfort. The sensation also varies a lot by area. Underarms, bikini line and upper lip tend to be more sensitive because the skin is thinner and more nerve-rich. Legs and arms are usually much easier. For sensitive areas some providers offer topical numbing cream applied about thirty minutes before the session which takes the edge off considerably.