A federal statute must be approved by both houses of Congress and be either approved by the President or repassed by Congress over his veto.
Joint resolutions can amend or repeal statutes, and vice versa.
As long as they are passed by Congress and approved by the President, both become statutes. Nowadays, federal statutes are designated first by the number of the Congress that passed them, and then in order of their approval. For example Public Law No. 100-1 is the first public statute the 100th Congress enacted into law. Prior to 1957, chapter numbers were used to designate statutes in order of approval, public and private laws being in one chapter series. 682, 57th Cong.