H. J. RES. 144 is a joint resolution that allows Congress to reject a specific rule proposed by the Bureau of Alcohol, Tobacco, Firearms, and Explosives within the Department of Justice. This rule concerns the definition of what it means to be "engaged in the business" as a firearms dealer....
Simple Explanation
Congress wants to stop a new rule from being used that changes who is considered a person selling guns as a business. They're using a special power to say, "No, we don't want this rule."