Settings are a very powerful part of the system, allowing to centrally control and configure a group of Terminals.
Terminals are attached to a Settings record and the Settings record is used to define the characteristics and options of the terminals. For example:
For the most part, you will have a Settings record for each store location (or group of stores in close proximity).
What makes the Settings object very powerful is that you can simply create another Settings record if you need to vary a group of terminals for any reason. For example, you could have a group of Terminals in your store that take credit card and cash and also some mobile Terminals that take only credit card.