Savant syndrome refers to children with neurodevelopmental disorders, notably autism, who demonstrate remarkable skills in a certain area.
This can include an extreme talent for drawing or any other type of artistic creation, an exceptional musical ability or exceptional calendar calculations. One of the most popular depictions of a savant would be Dustin Hoffman's character, Raymond, in the movie Rain Man, and though he was also autistic, he functioned at a fairly high level.
The term savant comes from the French term “idiot savant” which used to refer to those who were extremely gifted in certain areas and who also suffered some degree of mental retardation. Though this term is no longer used because of its offensive nature, it's where we have derived the name savant syndrome.