A union is a group of people from the same job/trade that come together to achieve common goals such as protecting the integrity of its trade.
Advantages:
-workers experience more job security and stability
-file complaints with their union representatives, to take them to management
-guaranteed safe and friendly work envoironments
-steady raises and benefits, such as health care
Disadvantages:
-Strike
-financial hardship
there are much less disadvantages to having labour unions than there are advantages.