Somehow, I've never taken an entomology class. It's a personal failing on my part. Sections of classes I've taken covered insects briefly however, and maybe someday I'll take a real class on insects. For now, there are field guides, and the internet, to aid my very rudimentary knowledge of the insect world. I still find "bugs" of all kinds fascinating!
From what I can gather, this little guy is a Western Tailed-Blue Butterfly, in the order Lepidoptera (butterflies and moths) and family Lycaenidae, the gossamer-winged butterflies, which includes other blues, coppers and hairstreaks (which are all broad types of butterflies).