There are four basic communication styles: passive, aggressive, passive aggressive and assertive. Everyone has a unique communication style which may be a mixture of these four styles. People may change communication styles based on the environment, who they are communicating with, and their current state of mind. For example, someone who is a passive communicator at work may come home and assume an aggressive communication style with their family.
Passive communicators tend to defer to the wants and needs of others. They keep their feelings to themselves and often go with the flow.
While a passive communicator may try to avoid open conflict, they can end up feeling resentful towards others. Since they don't voice their opinions, their needs remain unfulfilled.