This is a vector imaging format used in the CorelDRAW editor. It has a template that can be applied for other designs, including styles, grid parameters, page layout and other parameters. The CDT template allows for the creation of several images in one style without changing the settings in manual mode.
DXF is a common format for Computer Aided Design (CAD). It is developed by Autodesk and it is similar to the DWG format but it is more compatible with other software packages since it is open documented.