In Buddhist understanding, merit accumulated through good action creates effects that ripple outward in ways impossible to fully trace — the good deed that becomes the encounter that becomes the decision that changes a life downstream. This is not karma as cosmic balance-sheet but as a description of how causality actually works in a world of interdependent beings. What you do matters beyond what you can see; the ripple of good action extends farther than you will live.
Each step builds on the last.