Ok, think TT (Throwback Thursday). In the not so distant, old days, editing was linear. You added one video clip to another in sequential order and going back and changing something, meant the entire sequence after your edit, meaning going forward, needed to be moved up as well. Think even further back to editing filmstrips: You took out a section of film you moved up the entire subsequent section to close the gap.
Today, all editing software is non-linear. Which mostly means that you can go into an edit totally unprepared and keep editing until you ‘strike gold’.