Starts the Sphereize Normals mode. Sphereizing the normals will add a target point from which the loop normals will point away from.
Starts the Point Normals at Target mode. Adds a target point that the loop normals will point towards.
Align Vectors will take a vector from the average location of the selected points to the target and apply that vector for all of the selected normals.
This is the opposite of Sphereize normal. While Sphereize normal is good for round things, point normals at target is great for object with concave features.