If you have an experimental procedure designed to answer the question "is the electron in the circle?" and you run it then you'll either get a yes or a no.

If you don't run it then the sentence "the electron is in the circle" will not be true or false. Instead, the electron will exist a sum of two components, one inside and one outside (each of those components could of course be decomposed further) and importantly, these will interfere with each other giving rise to behaviour that's empirically different than what we'd expect if we simply didn't know whether it was inside or outside.

Side note: this 'electron inside or outside the circle' example is mathematically cumbersome - would be much better to talk about the electron's spin being 'up' or 'down'.