the.com/walkthrough

means A step-by-step guide that leads you through a process or task from start to finish.

from A straightforward compound of 'walk' and 'through' — the metaphor of physically walking a route being extended to mean guiding someone through a procedure. The sense of walking someone through steps is old, but 'walkthrough' as a single word crystallized in the 20th century, first for guided tours or rehearsed run-throughs (theater and software testing both used it for 'dry run before the real thing'), later narrowing in gaming culture to mean a full guide through a game's levels and puzzles.