Is there any difference between ritalin (methylphenidate) and concerta ?

Both methylphenidate: Although both are methylphenidate, Concerta is a long acting form whereas Ritalin as you have written it is short acting. There is Ritalin la which is a long acting form however. Therefore, the only difference between Ritalin and Concerta is the duration of action.

Ritalin/Concerta: both belong to the Methyl Phenidate group of stimulants. Concerta is long-acting, while Ritalin (methylphenidate) can be immediate-release or slow release (Ritalin (methylphenidate)-SR).