With Select Time you can specify a block of time by dragging in the Key window.
When you have selected a block of time, then you can apply any of the following operations to the highlighted block (and any keys contained therein):
A beige bar between two yellow lines appears as you drag across the box grid of the Dope Sheet Key window.
If a highlighted track does not support time operations, time selection in that track is ignored.
After specifying a time range, you can perform other time- and key- related operations.