All believers are called upon to come alongside of each other in this way. A support group is a small group of people who intentionally gather on a regular basis to ensure this happens in their lives in ways and doses that might not naturally occur.
Usually the participants are going through similar difficulties. They may all be grieving due to a loss they have suffered. They may have experienced abuse or gone through divorce. They may be struggling with addictive behavior. Support groups should target in on a specific need so people can find points of identification with one another.