Double parton scattering (DPS) is the process in which one has two hard scatterings in an individual proton-proton collision. It can compete in rate with single scattering in certain kinematic regions and/or for certain processes, reveals new information on proton structure, and becomes more important as collider energy grows. I will give a broad overview of developments in the theoretical description of double parton scattering, beginning with the most simple "pocket formula" approach, and then progressing to the recent development of a full QCD framework for DPS. I will also discuss the construction of a new DPS parton shower based on this framework.