According to Wikipedia, concept art is a form of illustration where the main goal is to convey a visual representation of a design, idea, and/or mood for use in films, video games, animation, or comic books before it is put into the final product. Concept art is also referred to as visual development and/or concept design. This term can also be applied to retail design, set design, fashion design and architectural design.
www.conceptart.org is the house of concept artists from all over the world and it has lots of galleries, a forum to share everything about it. There are also information about education of concept art, workshps and other related events.