A drawing hand is a hand that is not good yet, but might be a good hand after the next card.
For example, if you have four cards in a row that can be a stright or a hand containing four cards of the same color and that can provide a flush if the next card is the same color.
Ex. HJA-hjQ on hand and hj3-hj8-kl9 the flop. If you are betting with a draw due to several factors, especially how relationship between short odds and pot odds .