Timelines

Timelines are a concept used in a few worldframes.

Mechanics
Under the rules of these worldframes, the moment a decision needs to be made, time is split between one where one decision is made, and the other where the other decision is made. A few of these are inconsequencial - one person deciding between two different kinds of food is not going to cause enough of a deviation between the splitting timelines.

This leads to the flow of time looking like a nearly-infinitely spreading tree, were it to be graphed out.

Alternate dimensions may initially be confused for alternate timelines, but this is not the case. While some dimensions may show a deviation from another one at a certain point in both their timelines, this is merely a coincidence, and the decisions of all dimensions are factored into timelines.

Time Hopping
Time hopping is an unusually rare occurance. Occasionally, an entity will be able to jump between timelines. This, despite what it says, doesn't cause alterations on the current timelines, it merely creates two extra timelines, one where the entity decided to jump from (and its counterpart, where they decided not to), and one where the entity suddenly appears (and its counterpart, where the entity didn't appear).

TL;DR
Time's weird.