These are driving regulations based on your location. Most countries around the world have adopted one set of standards or the other, and for headlights to be street legal they must meet and be marked with the regulations adopted by that country.
DOT regulations are created by the United States Department of Transportation, for use in the U.S. & Canada. Meeting DOT lighting standards guarantees your lights are federally compliant in the United States for visibility, durability, and reliability to secure the safety of others.
ECE regulations come from the United Nations Economic Commission for Europe. ECE versions feature DRL & FP functions. ECE-compliant guarantees your lights are compliant in the European Union and in non-European countries that have adopted ECE Regulations for visibility, durability, and reliability.