If you don’t have enough to cover the bets and raises, you are said to go all-in, and are simply contesting that portion of the pot your money covers. Others who are active in the hand can still make wagers, but those bets constitute a side pot. At the hand’s conclusion, the side pot is decided first, then the main pot. You are not eligible to win the side pot since you invested no money in it, but you can win the main pot.
