Range markers are essentially two location markers that appear in the Range Markers ruler, and are grouped together to mark the beginning and end of a section in the timeline.
Creating a new range can be done by right clicking on the Range Markers ruler at the top of the timeline, then selecting New Range. Two markers with the same name and opposign arrows will appear along the ruler.
It is also possible to create range markers from a selected range or region in the Editor window, or to using the Ranges & Marks List in the Editor list.
Both markers of a range can be independently moved along the timeline by clicking and dragging them to the desired location.
They can also be moved together by dragging one marker.
See Moving markers for more information.