Glueless, explained
Glueless has become a marketing word. Used properly it means one thing: the wig stays on without adhesive, because it was built to. Used loosely it means "you could probably get away without glue" — which is not the same promise.
What makes a wig genuinely glueless
Three things have to be true. The lace is pre-cut, so there's nothing to trim. The cap has adjustable straps, so it tightens to your head rather than relying on tack. And the construction holds its shape without tension — combs and a band doing the work adhesive would otherwise do.
What you gain
Time, mostly. A wear-and-go install is minutes, not an appointment. But you also stop putting adhesive on your hairline repeatedly, which is the part of wig-wearing that does long-term damage to the hair you already have.
What to check
Ask whether the lace arrives pre-cut, and whether the cap adjusts. If a listing says glueless but ships with adhesive in the box, that tells you which definition is being used.