Casino chips are the tokens that stand in for money at gaming tables. Counting, checking and passing banknotes across the felt would slow every game down, and mixed currencies would make it worse; chips solve that with standard sizes and values that dealers can read at a glance.
Each denomination has its own colour, so a dealer can tally a stack in seconds. Colour schemes vary between casinos, and many venues issue their own branded chips that are only valid on their premises. For very high stakes, casinos also use plaques: larger rectangular pieces with much higher values.
Players buy chips at the table or the cage and cash them in at the cage when they leave. Swapping small chips for fewer high-value ones is called colouring up, and promotional non-negotiable chips can be bet but not cashed. Online, chips are purely visual, but the same denominations shape how table games present bet sizes.