The end step, often referred to as the "end of turn" and previously known as the "end of turn step", is the first step of the ending phase. It is usually the last opportunity for a player to perform any action before the next player's turn starts.  
From the Comprehensive Rules (Khans of Tarkir)
- 513. End Step
- 513.1. First, all abilities that trigger "at the beginning of the end step" or "at the beginning of the next end step" go on the stack. (See rule 603, "Handling Triggered Abilities.")
- 513.1a Previously, abilities that trigger 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. Second, the active player gets priority. Players may cast spells and activate abilities.
- 513.3. 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.")
The end step was magicthegathering.com's theme for the week of Aug 28th, 2006. It was chosen by Anthony Alongi to announce his departure from the site.