About Men In Black

I have never watched this movie.But, I've been interested in this movie.As I have heared that this movieis very funny.During I watch this movie,I felt terror.People who spend ordinary life changed incredible because of being attacked from arien.If they were in this real world....it's very sceard.I couldn't watch this movie,but little arien which is in the dead people said"orion belt..."I want to watch this movie until finish. I can't understand all phrases or words in this words.And, there are many words which I have never heared in daily English conversation.Are they native words? Are they slang words?:)