Etale cover - open cover analogy
Grothendieck and Artin introduced a generalisation of the notion of topology to study more general notions of sheaves. In this video, we motivate the conception of a Grothendieck topology by seeing how etale covers are like open covers. We look in the simple example of the Mobius band to keep the exposition elementary. It gives a foretaste of the ideas that come later in the playlist.