C is a procedural programming language which is widely used in embedded systems. PLEASE NOTE: Arduino is typically programmed in C++, not C.
The C programming language is the (direct or indirect) predecessor of many modern programming languages, although it is still actively used and developed. It is very similar to C++, except that C is not object oriented. That is, it will only support simple data structures which have no member functions.
Note: Arduino is usually programmed in C++, not C.
Please do not use this tag to indicate a general programming question. You may want to consider using the programming tag instead.