Minecraft wiki entry for Hopper, associated text: A hopper first attempts to push any items inside it. Afterwards, it checks if the block above it is a type of container. If so, it attempts to pull from it. Otherwise, the hopper attempts to collect item entities. Notably, hoppers can push to and pull from other hoppers, forming hopper pipes or hopper chains, which allow transporting items across several blocks and are further discussed below.