A projection is a way to translate the curved surface of the earth (3D) onto a flat map (2D). The challenge is that every map projection has distortion because the spherical nature of the globe cannot be perfectly represented in a two-dimensional map.

If you are interested in further discussion on projections check out the National Map website: https://nationalmap.gov/small_scale. Knowing the projection of your data is important especially when working with data that is part of a dataset that is larger than just your county or state.

This task sheet will cover how to change the projection of an existing file as well as enabling on the fly projection in QGIS.