Sequencing is a very important part of plot, conflict and theme development in literature. Thus it is also important to character development since much character development comes from plot complications and resolution. "Sequence" is defined as "an arrangement of two or more things in a successive order" (Collins Dictionary). Sequencing is how events in the plot complications, conflicts and resolutions are arranged in successive order.
Some works are not sequenced in chronological order. This is because some sequencing is interrupted by flashbacks and flash-forwards. Flashbacks provide "backstory," or what happened before we meet the characters. Flash-forwards give a glimmer of future potentialities, in other words, of what might happen. These flash-forwards can be good or bad. They often help build suspense and a feeling of dread or, conversely, complacency (watch out for the plot twist after complacency!). Modernists violate chronological sequencing intentionally. They do this to create a sense of fragmentation in time, perception of reality and characterization.
Using "Contents of a Dead Man's Pocket" as an illustration, sequencing is important in chronology and in flash-forwards. The sequential description of his actions and thoughts at the beginning of the story build interest and a sense of impending trouble. The sequential detailing of every minute action Tom takes builds suspense. The flash-forwards to the potentiality of falling to his death adds further suspense and horror while building deep sympathy with him.
He saw himself falling with a terrible speed as his body revolved in the air, knees clutched tight to his chest, eyes squeezed shut, moaning softly.