There is only one God (Allah) who is the true God and Islam is the submission to Allah’s will.
Allah created the world. Angels are the messengers of Allah, they are sinless beings created out of light. Of the four archangels Gabriel was the medium used to reveal Allah’s words to Muhammad.
The devil is called Shaitan or Iblis and is a fallen angel. Other beings are called jinn and they can be either good or bad and they inhabit the human world.