I assume you mean rvk's answer (cause you didn't clarify that!). It's used for example for the event system inside Lazarus. The lfm file contains the name of the event handlers (e.g. OnCreate = FormCreate to assign FormCreate to the event OnCreate) and when reading the object stream MethodAddress is then used to retrieve the address of the event handler's method (in this example the address of FormCreate). MethodName on the other hand is used for the inverse, namely when you serialize a descendant of TComponent to an object stream. The stream writer gets the address stored in the event handler (e.g. OnCreate), passes that to MethodName and then writes the returned name to the object stream (in this example this will be FormCreate again).
MethodAddress and MethodName work for any method declared in a published section, but you can't get any method signature (so you need to know that at compile time).