Why in the world of blue **** would we need eight different words for the same thing? What you have there is some political philosophies, a side of the political "spectrum", a political party, an economic system and a sociopolitical movement that came and went a hundred years ago. That you can't tell them apart is YOUR failure.
The reason why there are so many ways to describe a lefty is because lefties have hijacked all these terms at some point in order to pass themselves off as something better than the commies that they are. Sometimes they show up as Republicans like Romney, McCain, and Paul Ryan, but sometimes they call themselves libertarians. The more honest commies are the ones who admit to being socialists, progressives, or democrats. I have less against you as a commie than I have against commies who try to present themselves as conservatives.