Raststätte offers full motorway services
A Raststätte is normally reached directly from the Autobahn and may provide fuel, food, toilets, shops and other facilities without leaving the motorway network.
Autohof is usually just off an exit
An Autohof is a privately operated service area near an Autobahn junction. It can be a useful alternative for fuel, meals and longer breaks.
Parkplatz is for shorter stops
A Parkplatz is a simpler rest area intended mainly for parking and a short break. Some have toilets, while others offer few or no additional services.
Plan fuel before the tank gets low
Distances between major service areas can be significant. Refuelling before the warning light appears gives you more choice and reduces unnecessary stress.
Service areas on the Autobahn
The Autobahn has an extensive system of service areas (Rasthof, Raststätte) generally spaced between 40 and 60 kilometers apart. These usually feature a filling station (Tankstelle), restaurant or snack bar, convenience store, telephones, and restrooms. Many service areas also feature hotels, showers, playgrounds, conference rooms, and chapels. There are over 700 service areas in operation and they're open 24 hours a day.
Signs announcing the approach of a service area give the name of the service area, the distance to it, and one or more pictograms indicating the services available there:

Service area approach sign. The white sign at the bottom
indicates the distance to the next service area.
Smaller parking areas, many equipped with restrooms (WC), are even more abundant along the Autobahn. These are marked with signs like the one below.

Approach sign for parking area with WC
The past couple of decades has seen the proliferation of service facilities (mainly filling stations and fast-food restaurants) just off Autobahn exit ramps. Especially increasing in popularity are truck stops (Autohof). These generally offer facilities comparable to the service areas, but usually at considerably lower prices. Most are now marked by special signs on the Autobahn like the one below.

Autohof announcement sign
Service levels vary from stop to stop
Do not assume every rest area has fuel, food and toilets. Check the pictograms on advance signs before deciding where to stop.
Electric charging is increasingly common
Many larger motorway service areas now provide EV charging, but availability and charging speed vary. Plan charging stops before long motorway stages.
Truck parking fills up in the evening
Large service areas can become crowded with heavy vehicles late in the day. Passenger-car spaces are separate, but entrances and exits may be busy.
Hotels near exits can be cheaper alternatives
For an overnight stop, leaving the Autobahn by a few kilometres can provide more hotel and restaurant choices than a motorway service area.
