Services are buildings that are essential for fulfilling Sims' needs. There are eleven services: Power, Water, Sewage, Waste Management, Government, Regional, Fire, Police, Health, ControlNet and Drones. When first starting Sims will only demand a few services, as you level up ou will unlock more services and sims will demand those. There are 3 types of services, the first type are ones that require a certain amount of capacity depending on the demand, these include Power, Water, Sewage, Waste Management, and Drones. The second type are ones that have a certain area of coverage. These must be placed near the residential zone in order to function. These include Fire, Police, Health, and ControlNet. The third type are ones that function differently. These include Government and Regional. Service buildings cannot be stored except for the Eco Power Plant.
Each service has multiple buildings to choose from with varying costs of Simoleons and efficiency depending on it's size. There are 2 services specifically for OMEGA Zones. These are ControlNet and Drones, they cost NeoSimoleons. The Government service is not used to supply anything to Sims but rather useful buildings for your city. The Regional service is exclusive to Regions. It replaces the Government service. It has 3 buildings used to supply Sims needs in Regions and 1 building used to get an extra 20 storage.
If a residential zone does not have a service it will eventually get abandoned causing a population decline and lower tax revenue. If an OMEGA Zone does not have ControlNet it will instantly be abandoned.