A fairly dumb question...

[eluser]Negligence[/eluser]
Basically, yes.

--> is used for objects (instantiations of a class), while :: accesses a classes' methods directly without the need for an object. You can use :: to access non-static methods, but static methods must be called with ::.

I would recommend reading the OOP section in the PHP documentation. This is pretty basic knowledge you should have.