This document provides essential hotkeys for Mac OS X and Xcode. For Mac OS X, it lists common keyboard shortcuts like command-x for cut, command-c for copy, and command-v for paste. It also covers using command-space for spotlight search, command-w to close windows, and command-q to quit applications. For Xcode, it outlines shortcuts like escape for auto-complete, command-enter to build and run, command/ to toggle comments, and option-command-up arrow to switch between header and source files.