“Pura vida” is a Costa Rican regionalism that reflects how Ticos prefer to perceive life. Literally, it means “pure life” but the significance is more profound.
Ticos (yet another regionalism; “Costa Ricans”) use “Pura vida” to express a wide range of emotional statements and questions, applied the right intonation. A simple hello, could be answered by a “Pura Vida”, or just using it to say hello instead. And yes, you can ran into someone and just ask “Pura vida?” and expect an affirmative answer, “Pura vida!”. It can be used even as a sarcastic or ironic statement or question. You can use it if you are a bit upset or gloomy and trying to make the best out of it. As well, you can describe something that is really enjoyable, nice and cool as something “Pura vida!”, like “Powoweb is pura vida!”.