both seem to translate to "maybe" or "perhaps". When do you use the two words?

Una buena pregunta. No sé la respuesta, pero nunca he oido "tal vez" sin otras palabras (pues, casi nunca), pero a menudo he oido "quizá" (o "quizás") solo. A good question. I don't know the answer, but I've never heard "tal vez" without other words (well, almost never), but I've often heard "quizá" (or "quizás") by itself.

I understand them to be the same. "Quizas" may be a little more poetic than conversational. "A lo mejor" also means "maybe." And I also hear a lot from Colombians "de pronto" and from Peruvians "de repente." (I live in South Florida and speak Spanish fluently as a second language.)

Tara, I'm not sure whether you're saying that "quizás" is a little more poetic than "tal vez" or than "quizá." I hear "quizás" and "quizá" a LOT in casual conversation, so I don't think of either of them as being more poetic than conversational. I've also found that both pronunciation and word choice is often influenced by where someone is from.