Difference between web services and web application

Question

Lets have an example scenario:

Client opens a web site and finds the sum of two numbers which he enters from the textboxes.Then clicks on the ADD button.Two parameters a

Answer 1

To add 2 no.s we write a web service, to subtract we write a diffrent web service, however calculator is an web application that uses add,subtract and many other webservices in combine.