Non-negotiable chips, or NN chips, look like ordinary casino chips with one key difference: you cannot exchange them for cash. They exist to be wagered, which is why land-based casinos use them for promotions, handing them to loyal players or to customers who have been playing for a while. A player can then bet them at a game such as baccarat.
In most programmes, an NN chip stays in play until it loses. When it wins, the payout comes in regular, cashable chips, and the player keeps the NN chip for the next bet. The rules on where and how you can use them vary by casino, so ask the staff first. In some cases, players buy NN chips, always at face value, so a 10,000 chip costs 10,000. That fixed value is where the name comes from.