The charging station gives a robot the ability to charge itself autonomously (it can just drive itself onto the top of the charging station).
The fast-charge stations can be located in a place with a sufficient power supply. For example, if you want a battery with some capacity to charge in 30 minutes, you have to have more power than the one that can charge it in 90 minutes.
Robot charging stations require a lot of power, and 90% of the facilities we put them in will need special wireworks for the charger.
You can find the charging station area at the bottom-left corner of the Structure page at the Areas bar. When you click it, the charging station will be highlighted on the map.