It’s pretty simple: it is a legal right workers have when two or more decide to join together for the purpose of collective bargaining. The right extends to most industries, though some have separate laws that govern their organizing.   Once your union is recognized, the employer has a legal obligation to bargain in good faith on the terms and conditions of employment.

“It is hereby declared to be the policy of the United States to eliminate the causes of certain substantial obstructions to the free flow of commerce and to mitigate and eliminate these obstructions when they have occurred by encouraging the practice and procedure of collective bargaining and by protecting the exercise by workers of full freedom of association, self organization, and designation of representatives of their own choosing, for the purpose of negotiating the terms and conditions of their employment or other mutual aid or protection.”  National Labor Relations Act, Section 1