見る, as the more basic and general みる, can be used more broadly, but 観る is typically used for observing or viewing exciting or interesting things. You can say 映画を観る, where as you would not use 観る for just plain looking in general.
There are other nuances of みる expressed with other kanji as well. 診る, 視る, 看る, etc.
For most instances of everyday looking at things, 見る is the right one to use, and because it’s general, no one will really get on your case about saying 映画を見る either, even though 観る is used a lot there.
FYI, that appears to just show an all encompassing list of みる definitions, ignoring kanji nuances.