S. J. RES. 100 is a resolution in the Senate that seeks congressional disapproval of a rule set by the Environmental Protection Agency (EPA). This EPA rule relates to the "New Source Performance Standards" and "National Emission Standards for Hazardous Air Pollutants"...
Simple Explanation
S. J. RES. 100 is about Congress wanting to stop a new rule from the EPA that would make certain factories that make chemicals and plastics follow stricter pollution rules. If Congress agrees, these new rules would not happen.