i've got a couple acquaintances associated with it
it's not a formal, centralized organization - just a loose array of groups identifying with the concept of antifa, ideologically leftist (usually left-anarchist, though tankies and more garden variety leftists may also be affiliated with or have chapters), united by opposition to "fascism," the definition of which (and praxis with respect to "fighting" it) really varies from chapter to chapter, individual to individual, because again it is not a centralized organization
How is silencing speech with violence not fascism?