Good job! In Part 1, we mentioned that there are two PostGIS column types: geometry and geography. Back then, we said that both of these types can be used to do similar things but that geometry is quicker, whereas geography is more accurate. We could actually stop right there and say that this is sufficient for you to be able to work with geometric and geographic data.

Still, some students are eager to know why there is a difference in performance and accuracy between geometry and geography. Let's throw in some theory, then.