The Planning Section simply documents everything that has happened on the incident, and projects and forecasts what will hopefully happen in the future, including the incident goals.
The Resources Unit maintains the resource status of every piece of equipment on the incident. They also provide technical specialists including archeaologists, geologists, forest/environment specialists, etc.
The Situation Unit keeps tabs on the incident itself. It is kept up to date as best as possible from the fire line reports. They provide the Public Information Officer the actual fire information. Sometimes the communications takes 8 hours to reach the public from the fire line. A fire can more than double in 8 hours.
The Documentation Unit provides the paperwork and clerical needs of the incident. Every last log entry is recorded for each incident.
Demobilization Unit specializes in cleaning up after the incident. While the fire is long out, these people are still checking engines out and just now starting to figure out what rehabilitation is needed for the environment at the incident etc.