There is no legal difference between a "joint resolution" and a Bill. Both must be passed, in exactly the same form, by both Houses of Congress, and both must be presented to the President and signed by him, repassed over his veto, or remain unsigned for ten days while Congress is in session to become a Law. Laws enacted by virtue of a "joint resolution" are not distinguished from laws enacted by a Bill.
Joint resolutions are generally used to authorize small appropriations, to enact continuing resolutions that provide for government expenditures in the absence of an overall appropriations law, to create commissions or other bodies, or to extend legislation already drafted. They have also been used to annex formerly independent nations including Texas and Hawaii without a treaty.
Joint resolutions are also used by the Congress to propose Amendments to the Constitution of the United States. These joint resolutions are not distinguished by bill number, but they do not follow the process outlined in the cases of a Bill. Article V of the Constitution requires the Congress to present any proposed Amendment to the Constitution for ratification as a part of the Constitution directly to the States, bypassing Presidential approval or disapproval.