It is used for moving cowgirls, bees, and rockets. It works more or less like a hovering hand, but it uses electricity. You control left click to set source, control right click to set target, and then after being placed, it will move things from source to target as long as it is connected to electricity and there is enough electricity in the network.
A use case for the crane is for automating item transportation using rockets. You can make it move rockets from one silo to another, so that the same rocket can be sent back and forth.