There are two ways of doing it. The way most people use most of the time does not, it's statically dispatched. The other way is dynamically dispatched, though there are some differences from the way that C++ virtual works. They should be roughly the same in that case, though.
It depends, you have access to both capabilities. By default if you're only dealing with an impld trait then it will use static dispatch. If you are passing around that same object as a trait objects, it will use dynamic dispatch and you can also impl Traits on other traits, which are always used as trait objects (vtable) but that have some restrictions on what they can look like. If you rely on the Deref trait to make it look like you have inheritance (but in reality it is composition) it will be the same as the later using dynamic dispatch.