There are some basic questions that get asked and answered again and again. Over the past year, I've gone through a bunch of tags to collect and close as duplicate many of those towards Canonical Question/Answer pairs. I'd like to collect these here, in order to have a handy list of questions to use as a "duplicate master". Also, these questions should be scrutinized over frequently, in order to update their content to maintain their quality and relevance.
Please help to maintain this list of Canonical Questions and Answers!