A more thorough explanation:

Definition: Union certification is a decision made by the National Labor Relations Board or a state agency that confirms a particular union as the bargaining representative for a group of workers in a company. This decision is made because the union has the support of the majority of workers in that group, which is called a bargaining unit. Union certification is also known as certification of bargaining agent or certification of labor union.

Example: If a group of factory workers decides to form a union and hold a vote, and the majority of workers vote in favor of the union, the union can apply for union certification. If the National Labor Relations Board or a state agency confirms that the union has the support of the majority of workers in that group, the union will become the official bargaining representative for those workers.

This example illustrates how union certification works. When a union is certified, it has the legal right to negotiate with the company on behalf of the workers in the bargaining unit. This can include negotiating wages, benefits, and working conditions.