what is method overloading and method overriding?

Refer this link.

 

http://www.c-sharpcorner.com/UploadFile/0c1bb2/method-oveloading-and-overriding-C-Sharp/

When you change (override) the implementation of the method as defined in the base class in a derived class it is called - overriding. 

 

When you write several methods of the same name (changed by having different method signature, for example, number of parameters, etc.) that is called - overloading.

 

Google 'method signature' for details.