Blenders have different speeds for a variety of blending options, some blenders can even chop as well as blend, If you are making milk shakes you should put the ice cream and milk and whatever other flavors you want in the shake and you should blend them on high so you get a nice thick shake.
Some blender speeds crushes, blends, mixes, fluff, whips, and so many more things that they do. For making milkshakes I would use the blender speed that blends at first and then the one that mixes.
