Seriously gel and acrylic are pretty much the same. Gel usually has to sit under a UV lamp to cure.
Powder gel application is a little bit different in that you paint stuff on the nail and then they usually sprinkle the powder over it to mix it.
Gel is a gel form that is premixed in a container and actually looks like gel.
Acrylic is powder and liquid that has to be mixed together and then applied to the nails.
Hope that helps a little. There really isnt a huge difference in any of them