A tester is an 100% genuine product that is unused and unopened.

Testers are the regular products usually without the fancy packaging in a plain box (so don't make such good presents - but are an ideal refill for yourself) generally they are also marked tester on the bottle, they are always new and unused; and sometimes come without a lid.

As they don't have all of the fancy outer packaging we get them at a better price, so are able to sell for less.