A union is a group of employees in which a majority decide to bargain collectively to try to improve wages, benefits and working conditions. They can do this independently or with the help of an established labor organization.
Basically, you sign a "union card" (a card that indicates that you would like to form a union at your workplace). If a majority of employees sign such a card, the cards are given to a government agency (The NLRB - The National Labor Relations Board) which then schedules and oversees a secret ballot election to see if the employees really do want a union. If a majority votes "Yes" then a union is formed, with which the company must bargain over wages, benefits and working conditions.
The primary objective of a union is to secure a contract which spells out the wages, benefits and working conditions for employees. Once a contract is signed by the employer and ratified by the employees, the union then exists to help any employee who wants such help to smooth over problems with management. This is done through the grievance procedure.
The grievance procedure is a procedure spelled out in the contract that explains how any conflicts between employees and management is to be resolved. Basically it works as follows: Let's say you've been written up for something and you feel it isn't fair. You talk with your managers but they refuse to do anything about it. You then go to your shop steward (see below) to get help. The steward sits down with you and management and tries to resolve the issue. If it can't be resolved at this meeting, a business agent for the union (see below) will come to the store to talk with management. If they still cannot resolve the problem to everyone's satisfaction, the business agent will appeal to upper management. If this step fails, both parties will bring in a neutral arbitrator who will issue a final decision.
The company and the union put teams together. The company's team is usually comprised of lawyers, local management and upper management officials. The union team usually consists of bargaining unit (see below) employees, lawyers, and union negotiators.
Before contract talks, the union passes out a form on which you list those things you'd like to see in a contract. The union uses this to base the negotiation on. Furthermore, you could be on the negotiating team, but at the very least you get to vote on the contract. If a majority doesn't approve of the contract, the negotiating team has to go back to the drawing board.
The bargaining unit defines which employees are eligible to vote for and be in the union. Excluded by federal law are managers and security guards.
You can vote any way you like in the election whether or not you signed a card. It's secret ballot so no one, neither management nor anyone else, will ever know how you voted. If you do sign a card but later change your mind and want the card back, you can do so by asking for it back in writing.
You'll be asked at some point to sign a union card. Once about 65-75% of the employees in the bargaining unit are signed up (legally, you could file with as few as 30% of employees signed up, but it's best to wait for a solid majority), the cards are submitted to the NLRB. (The National Labor Relations Board, the government agency that oversees union/management relations.) The bargaining unit (see above) is finalized either by the NLRB or by agreement between the company and union. An election date is set. The secret ballot election is held and a majority wins. Of course, during the few weeks before the election, both management and pro-union employees will try to disseminate information. Management will do this through mandatory meetings and memos in your mailboxes. Pro-union employees will try to get you to talk with them about concerns, hold voluntary meetings and may mail stuff to your home. Tensions may start to run high, but the best way to avoid this is by feeling free to talk with you coworkers about your concerns.
Information courtesy of Shannon Matthews