What I want to know about my topic

There are a lot of questions that i have about Horror movies, but i only have a few that i really want to know. My essential question is what is the history of horror movies? My first specific question is why are certain horror movies popular even today? My second question is how do the writers think so creatively? My third question would be how do the movies get so scarry? My forth question is how the special effects play a part in making these movies look good?. My last question is what is the 1st horror movie ever?