I've been trolling a scary and stupid FB site called Humane Watch. They claim to be a "watchdog" of the United States Humane Society (the group that makes many rescues and almost all local animal shelters possible). What they really are a bunch of ignorami, who don't get the Constitution, and don't understand that what they hate are administrative agencies. So, here are the very bare bone basics, I don't have desire or interest this evening to get into the depths, but I will do so at some other time.
We have three distinct branches of the US (and most state) government(s): executive, legislative and judiciary. From the legislative branch, we get administrative agencies that are created by acts of Congress to carry out specific legislative purposes and goals. Examples of these include the EPA, the SSA, the VA, and so on. This is the basic purpose of agencies.