DDS is a file format created by Microsoft for use in their Direct X SDK (Software Development Kit.) Direct X provides a library to standardize and ease the development of 3D applications, such as games. GIMP is a free image manipulation software similar to Photoshop. GIMP cannot create or open DDS files by default. You need the gimp-DDS plugin to do so. Writer Bio

How to Install a DDS Plugin for GIMP  9 Steps  - 71