The Create Baking Render Target option create a new Render Target set to use an OSL Baking Camera complete with a custom OSL script designed for texture baking (figure 1). This render target is identical to a regular render target with the Camera option set to OSL Baking Camera. The difference is the custom OSL script generated to assist with texture baking using an OSL camera. More information can be found in the OSL Baking Camera section of this documentation.
Figure 1: The default OSL script included when using the Create Baking Render Target