They are the ultra- extremist element of the ultra- far- left.
They seek to destroy American society in the hopes of building a new one that's a mixture of Anarchy and Communism.
Their positions on all issues (I speak as someone who has visited their websites for laughs, and as someone whose brother was once involved with similar groups many years ago) are extreme left- wing.
They are usually spoiled trust- fund brats between the ages of 15 and 25 who hate their wealthy suburbanite parents but still happily take as much money from them as possible.
They rant about the evils of capitalism and "Corporate greed" while tweeting away on their current- model Iphones.
They latch onto any liberal protest movement that they think will enable them to spread violence and chaos under such euphemisms as "Direct actions" and "Diversity of tactics," and are pretty much always the first to get violent in such protests.
Fortunately, they do not have the brains, charisma, work ethic or self- discipline to advance their goals any farther than starting the occasional riot.
Unfortunately, the Left usually responds to their violence and lawlessness by either ignoring them, claiming that they must REALLY be "Agent provocateurs" planted there by the police to make the protest movements in question look bad, or portraying them as wonderful, misunderstood heroes taking a righteous stand for "Social justice" who would never hurt a fly. I've seen the DUmmies use each of those responses in past DU threads.