Digital Multimeters: Voltage
An electrical pressure difference exists when there is a mass of electrons at one point and a deficit of electrons at the other. Like the difference between a battery's positive and negative battery posts. Voltage meters measure this difference. They can be analog or digital. A digital multimeter measures electrical properties like voltage, resistance, and current.
High-end multimeters usually have an auto-ranging feature. They have a single DC position and automatically find the best range for the voltage measurement. A manual meter has more setting options, and you set the meter to the lowest range setting that does not "OL" or over-range the meter. It also has AC and DC voltage settings. For testing an automotive 12-volt battery, it is typically the DC 20V setting.