Magritte is a surrealist artists. These are the artists who explore dreams. Often times, they use symbolism as a design language. Think as visual codes to infer meaning upon their audiences. For example, in the self portrait below, the fruit is symbolic of knowledge from the garden of Eden, and the fact it is hiding Magritte's face is symbolic of the shame Adam and Eve felt after eating of that fruit.
Like dreams often seem to blend reality with the mysterious fog of the nonsensical, surrealism often questions our perception of reality. Reality like ogres and onions is layered. Paintings like the one below play with questioning that reality. True that is not a pipe, but what is it?
Surrealists are often playful and have inspired many forms of media.
Robert Gonsalez is an artist inspired by Magritte who is a commercial Surrealist. His work is found in books, magazines, and many forms of advertisements.
There is even surrealist photography.