Actor Crispin Hellion Glover’s controversial (most of the actors have Down syndrome) directorial debut, “What Is It?,” finally arrives in New York. Difficult to describe, the film (pictured above) is, according to Glover, “the adventures of a young man whose principal interests are snails, salt, a pipe and how to get home.” The screenings, at 7 p.m. today, tomorrow and Sunday at Anthology Film Archives, will be accompanied by an hourlong slide show narrated by Glover and a Q&A session with the director. The Anthology is at Second Avenue and Second Street; (212) 505-5181.