What is a difference between a method and a function?

What is the difference between a method and a function? Is it that a method returns a value and a function doesn't?

Method is actually a function used in the context of a class/object.

When you create a function outside of a class/object, you can call it a function but when you create a function inside a class, you can call it a method.

class foo {
   public function bar() { // a method
     ........
   }
}

function bar() {  // a function not part of an object
}

So an object can have methods (functions) and properties (variables).

The words are not opposed to each other but rather describes two possible aspects of a subroutine. An attempt to define the words follows:

Subroutine: A set of instructions that can be used several times in the same program.

Function: A subroutine that returns a value. Derived from functions in mathematics (wikipedia).

Method: A subroutine that belongs to an object or a class. Could be a function.

I tend to use the word "function" for every subroutine that has no side effects but returns one clear value and the word "method" for every subroutine that has a side effect.

The difference between the expressions "method" and "function" is that a "method" is a member function of a class, whereas a standalone function does not, and a standalone function usually exists in global context.

Both are used interchangeably, but function is the terminology used in structural languages and method is the terminology used in Object Oriented Langauages. Also methods exists within objects while functions can exist without objects as well.