S. 3963 aims to clarify that certain species that live entirely within one state's borders are not considered part of interstate commerce. These species, referred to as "intrastate species," would therefore not be subject to the regulations under the Endangered Species Act of...
Simple Explanation
S. 3963 says that animals or plants that live only in one state don't need special rules if they are not part of a big market that involves different states, so they wouldn't need protection from certain national laws. This means those local creatures won't get rules for protection unless they are important to trade between states.