No union can guarantee what will be in the contract—that is the product of negotiations. But unionized workers typically enjoy better wages and benefits than non-unionized workers.
After certification, an elected bargaining committee will engage in an extensive process to collect staff concerns through a survey process. This bargaining committee will represent different job titles and divisions. Any staff who are in the bargaining unit can run for election to the bargaining committee. This bargaining committee will be tasked with proposing and negotiating a contract that reflects the interests of the titles and divisions encompassed in the bargaining unit (staff in the union).