The common concept is that during each event/decision, there are an infinite number of possibilities. Each of those possibilities splits off into its own form of events, which in turn starts its own infinite cycle.
The definitive Alternate History author Harry Turtledove exploits this theory in his Young Adult novel series, in which someone has devised a way to travel sideways in time. Not to change events in their own timeline, per se, but to study the events of another timeline. This effectively eradicated all need for resources, because there is an infinite number of alternate universes, there is an infinite amount of petrol, wood, and other resources.
I'm reading a Harry Turtledove book right now in which Earth is invaded by aliens, During WWII.
It's really, really good.