A chip tray, also known as a rack, is a tray used to carry chips and tokens. Most casinos use chip trays made from clear plastic.
This is to prevent players from cheating at the table by hiding cards or any other forbidden items.
The main use of a chip tray is to make it more convenient for casino players to handle and carry chips around. This is because players often have dozens, sometimes hundreds of casino chips to account for when playing.
Instead of carrying them around in their hands or pockets and potentially losing them, a chip tray allows players to simply stack the chips in different compartments.