513.1. The end step has no turn-based actions. Once it begins, the active player gets priority. (See rule 117, “Timing and Priority.”)
513.1a Previously, abilities that triggered at the beginning of the end step were printed with the trigger condition “at end of turn.” Cards that were printed with that text have received errata in the Oracle card reference to say “at the beginning of the end step” or “at the beginning of the next end step.”
513.2. If a permanent with an ability that triggers “at the beginning of the end step” enters the battlefield during this step, that ability won’t trigger until the next turn’s end step. Likewise, if a delayed triggered ability that triggers “at the beginning of the next end step” is created during this step, that ability won’t trigger until the next turn’s end step. In other words, the step doesn’t “back up” so those abilities can go on the stack. This rule applies only to triggered abilities; it doesn’t apply to continuous effects whose durations say “until end of turn” or “this turn.” (See rule 514, “Cleanup Step.”)