One of my favourite educational YouTube channels SciShow recently posted a video on map projections. The video gives a good introduction into why we use map projections and explains how different map projections distort Earth, whether by area, shape or direction. We all know how much hate the Mercator projection gets for how it grossly distorts size, and I enjoyed how the video made note that the Mercator does have its positive aspects: maintaining shape and true direction.
SciShow focuses on the whole world in this video, but map projections are also an everyday consideration when making regional or local maps. You're probably not going to want to use the same projection to plot Russia, which mainly spans east to west, and Chile, which spans north to south.
What's your favourite map projection?