There are different types of boundaries, but their purposes are to allow us to remain safe, respected, and free of harm.  All boundaries remind us that the feelings, behaviors, and attitudes of others are separate from our own.  The feelings and thoughts of others are not our responsibility.  We can feel empathy for another person and show compassion, but we are separate from the other person.

One type of boundary is a statement or request that we communicate to someone.  The statement is usually a request for a particular behavior to cease or to be modified.  When we establish a boundary, we must be willing to follow through.  We must honor our boundary even if others do not.  For example, if we ask someone who is verbally abusive to stop the behavior in our presence, we must be willing to walk away from the person if he remains abusive.  We do not negotiate our boundary with the person.  We avoid haggling over why he does not honor it.  We state our boundary clearly and honor it for ourselves.

Source: pp. 346-347 of The Big Red Book of Adult Children of Alcoholics