Sebastopol is a city inside Sonoma County. The county and city are separate governments — each with its own budget, elected officials, and jurisdiction.
What Sonoma County controls: Unincorporated areas (outside city limits), the county jail, county roads, social services, public health, and many regional programs. The county also administers certain state programs (like CalWORKs and Medi-Cal) that flow to residents regardless of which city they live in.
The Board of Supervisors: Five supervisors, elected by district. Sebastopol is in the 1st District. The board meets weekly in Santa Rosa and has far more budget and staff than most cities.
Special districts: Your water may come from a water district. Your schools are run by a school district. Fire protection may be a fire district. These are separate elected governments with separate boards, budgets, and elections — and most people never know they exist.