Accumulation Is a Running Total
Accumulation means keeping a total while new pieces arrive. The pieces can be distances, quantities, areas or anything else that adds. The important idea is that the total itself changes as the endpoint moves forward.
Move the idea
Try it: change one value
Change one parameter and watch what changes with it.
An accumulated quantity is not one frozen answer; it is a running total indexed by how far you have gone.
Keep every earlier piece
A running total remembers what came before. Adding a new contribution changes the total from its previous value rather than replacing it.
The endpoint matters
Stop after three pieces and you have one total; stop after six and you have another. So the accumulated total can itself be viewed as a function of the endpoint.
Bridge to integrals
An integral is continuous accumulation: instead of adding a few discrete pieces, calculus adds contributions across a continuously varying interval.