Steps run in order.
An event's steps run one after another, each finishing before the next. A rule with a cooldown waits that long before it runs again, for everyone or per player.
If, and otherwise.
An If checks one yes-or-no value and runs its Yes steps or its No steps. Ifs nest. An If straight after an event is the rule's own check: the file folds it into the rule, and the canvas keeps it as a step.
Loops.
A For each runs its steps once per item of a list and names the item for the steps inside (each, unless you name it). A Repeat runs them a set number of times. Inside either, {index} counts the rounds.
Waits, random picks, and functions.
A Wait pauses the rule for some seconds while the game goes on, then continues where it was, even across a server restart. Pick at random runs one of its options. A function is a named list of steps that several rules run, with inputs of its own.