Have a look at these two claims about the morning and evening stars (Phosphorus and Hesperus):

Phosphorus = Phosphorus
Phosphorus = Hesperus

The first of these is bland and uninformative. The second is interesting, and indeed a genuine scientific discovery. Yet both these names refer to the same thing, namely the planet Venus.

So it must be that, over and above their reference, names have something else—something which we call, following Frege, a 'sense' ('Sinn').

By the way, Frege changed his mind about what is related by identity ('='). In his Begriffsschrift, Frege thought identity related names; later on, he held that it related not names but things. This video doesn't go into this in depth, but it's important to keep in mind.