"Nurd" is a slang term for someone who is considered unfashionable or socially awkward, particularly someone who is overly interested in computers or technology. It's often used playfully, but it can also be considered derogatory.
"Nerd" is a more widely accepted term for someone who is very knowledgeable and enthusiastic about a particular subject, especially computers and technology.
While "nurd" is sometimes used, it's not as common or as widely accepted as "nerd".