"BDU" stands for battle dress uniform. This includes military fatigues intended for training, combat, field work and as utility wear during deployment. As official uniforms, the use of BDUs is governed by rules issued by a commanding officer.
BDUs are largely outdated military apparel and only continue to be used in select sectors. The U.S. Coast Guard and the U.S. Air Force Civil Air Patrol, for example, still wear them. BDUs debuted in the 1980s and were the official combat dress of the U.S. Armed Forces through roughly 2005. The camouflage pattern was intended to provide cover in woodlands and was later altered to provide cover for desert regions.