The Justice League Cinematic Collection shows numerous dedicated superheroes that have joined the  founding members to fight crime and injustice, and act as Earth's first line of defense from terrestrial, extra-terrestrial and inter-dimensional threats.

In this Justice League group of superhero characters one can easily identify: Green Lantern, Wonder Woman, Cyborg,  the Flash, Superman, Batman, the Martian Manhunter. The last three superheroes  in the very background may be Black Canary,Plastic Man, and Black Lightning

The initial team first appeared in The Brave and the Bold #28 (March 1960). The team was conceived by writer Gardner Fox as a revival of the Justice Society of America, a similar team from DC Comics from the 1940s.

To read about the Justice League as presented in DC Comics go to this DC Comics post.

Or this wikipedia page titled: Justice League 

Or read about the Justice League in this article on GoMart.com: History and Evolution of JLA (Justice League of America)