Andy Pavlo's video lectures are very good. Watched both introductory and advanced lectures a year or so ago. Recommended. Previous videos may be found from the channel.
You usually use localStorage for e.g. user settings that are not stored on the server. There are many sites that give you the possibility to change a preference or two without the need for an actual account on the site. That sort of information is usually stored in one of the client-side storages.