What is the difference between webservice and webmethod?

A Web Service is application logic accessible to programs via standard web protocols in a platform independent way.

Web Method is part of the web service.

Web Service create webservice stack
web method is part of that stack.

we can call webservice by GET,POST , SOAP method
web method is call by proxy of web service
Web services can be created in .net and it can used be in java. So it is platform and languange independent.

Web Services provide a means for applications to communicate with each other in a platform and programming language-independent way. A web service is an interface of a software component which describes a collection of operations that can be accessed through XML messages.

Web method is a method in a web service.
Web method can be exposed when the web service is deployed.