Normally, garbage bags use flat seal with a straight seal along the bottom of a can liner. This type is for easier dispense and storage, and bottom sealing is 100% leak proof.
Another type of sealing is star seal for garbage bags. The bottom is sealed like in the picture below, like a star when blown with air. The strong point for this bottom sealing is leakproof, not allowing any escape of liquid. This allows the bag to easily conform to the shape of the container and distribute the weight of the contents evenly inside the bag.