Exchange of messages between objects, what does it mean?

For mainstream use is what everyone knows as invocation or method call. That is, you call a method and indicate what object you are referring to.

Smalltalk is that the language that originated the term uses it more correctly and has a more important meaning and has a more sophisticated invocation, delegation and non-existent method solution. That is, the object has an infrastructure to solve what it actually does. Flexibility is huge but performance is often poor.

Smalltalk is a language where everything (not just marketing) is an object, including the message and the classes themselves. this requires a great dynamism in the language.

The message passing usually occurs for a complete copy of the data that is great for competition but poor for resource savings, so it is something little adopted.

The term is little used in practice in languages such as Java, C # or C ++, which have a simpler mechanism and almost everything solved in compilation.

Wikipedia article .

The exchange of messages occurs through the call to the methods of an object by another object.