There are many meanings to the two types of hands or paths witches take in their magick, and it only makes me puke the amount of content on this topic. The reason is because it actually means several things at once to many different religious views and non religious ones so when you pin point only the main ones you still come up with a handful of material to read on. To be more specific i'm only going to cover the one i know about and leave you overachievers and readers my sources and sites i find are helpful in this topic to continue your quest in your pursuit of knowledge.
People have to find words to identify themselves and its no different with how we practice magick and how we identify ourselves with that. Like using the terms "white" and "black" magick to express what type of path were laying out or just in general using colors to represent magick we like. There is actually nothing wrong with that in my opinion, personally i was taught energy doesn't have a color and energy is magick, but to each their own. In this case the Left hand and Right hand signify the type of magick you cast as just one example . The Left hand in just about every corner of the world is the hand of evil so those castors practice black magick and from one of my reading materials you don't want to end up in that existence. The Right hand then follows as the counterpart and is the hand of the light and those people are generally more spiritually evolved and only use white magick for the good of the universe and all that honey.
Thats only one view of course feel free to drop your's down below and blessed be! -Baron