Slipping and Sliding
a scene set out of sequence in the past.
a scene set out of sequence in the future.
a section that suddenly thrusts the reader into the back-story, sometimes for a paragraph and sometimes for a longer stretch. (In Stephen King's Wizard and Glass, for example, the slip-back is over 400 pages).
a brief glimpse at the future, usually at the end of a chapter. For example, He left the apartment. He would never see it again.
like a triple lindy, this is a difficult progression of slipping further and further into the backstory, sometimes three or four layers deep, and climbing back out. It's difficult (I've done it, and hopefully well). King's most famous double slip back is in The Gunslinger, where he slips back twice in the story before regaining the current timeline.
Edward C. Patterson