Why A repeater listens on one frequency and retransmits on another, and the difference between the two is the offset. On 2 meters (144-148 MHz) the standard separation used across the US is 600 kHz, so your radio transmits 600 kHz above or below the repeater's output frequency. Which direction depends on where in the band the output sits, and most radios select it automatically from the band plan.
Watch out The 5 MHz figure is the standard offset for 70 cm (440 MHz) repeaters, not for 2 meters; 500 kHz and 1 MHz are not standard offsets on any common band.
2 meters: 600 kHz. 70 cm: 5 MHz. The higher the band, the bigger the split.