The term alt-left originated in response to the rise of the alt-right in 2016. It’s basically a mirror term used to define a group of social media-oriented extremists. These extremists have a real-world presence as well and have staged numerous demonstrations and sometimes violent protests.
The main extremist groups are Antifa, Black Bloc, Socialist Rifle Association, and various local communist groups, which vary from city to city. The pro-abortion group Jane’s Revenge falls into this category as do the militant trans-gender groups
Some of the main features of militant-left extremism are revolutionary marxist ideology, liberation theology, extremist environmentalism, anti-racism, and an idealistic worldview that their mass revolution will solve all the problems of their country.
The main targets of militant-left extremists are the police, Immigration and Customs Enforcement (ICE), various alt-right groups like the Proud Boys, and anyone they deem to be a “Reactionary” or “fascist.” Their targets constantly shift depending on current events and have lately included conservative supreme court justices who helped overturn Roe v. Wade as well as other well-known conservatives.