New Media refers to works that can be found originally on the internet
Subsets include Blogs, Web Animation, Web Comics, Web Games, Web Serial Novels, Podcasts, and Vlog Series. The Abridged Series, Let's Plays, and After Action Reports also tend to be New Media.
It is common for New Media, especially Web Serial Novels, to spawn Shared Universes as other would-be writers think the original work is pretty neat and contact the writer for permission to play in his/her sandbox.
Both Web Original and New Media are for works that originated online. The distinction is that New Media works allow for feedback and audience participation - if a work doesn't allow for this, then it's a Web Original, not New Media. However, when it comes to tracking these works by the decade they were first created, All The Tropes uses Category:Web Original by decade for both web Original and New Media.