Part of surrealism is blending shared symbolism with personal metaphors (reinforcing the "dream logic" that Feutus mentioned). So a gun on a table might illicit the same response from you and I, but an eggplant might mean something completely different. Because of that, often in surrealist works there's no "right" interpretation, just a personal response. Good surrealist works will inspire your subconscious to think or feel, whereas poorer works will seem like randomness for the sake of randomness. Contrast this with "outsider art", which is all about personal expression without the desire for communication. Surrealism is still talking to the audience, whereas the outsider has no interest in the audience. Connections, if they happen, are more by chance than by intent.
Also important to note, in the world of art, surrealism specifically grew out of Dada, which was highly political and confrontational. Surrealism expanded on the ideas and techniques, and the focus is a lot broader. Think early punk rock going into post-punk. Lots of shared elements, but creating very different expressions. Dada, because the focus is so much narrower, is a little bit easier to get a handle on, so it's a good place to start if you want to understand more about surrealism.
There is, by the by, some surrealist music out there too. Nurse With Wound is one of the more obvious choices. If you are interested in exploring surrealism more, check out the album "Spiral Insana". It's a good starting place, heartbreaking and exausting, inappropriately funny and schizophrenic, bordering on paranoid. Great stuff!
Oh, and hey, Songs from the Second Floor! I haven't seen that in a while, but I loved it!
Okay, enough pretentious artsy babble from me!
