This document discusses cross-platform mobile development and compares three cross-platform SDKs: PhoneGap, Appcelerator Titanium, and Adobe Air. PhoneGap allows developing hybrid mobile apps using HTML, CSS, and JavaScript and runs on many platforms but lacks native UI controls and GUI tools. Titanium uses JavaScript and compiles to native apps with better performance than PhoneGap but can be more difficult to adapt to different platforms. Adobe Air uses ActionScript 3 to create hybrid apps but also lacks native UI controls and may have performance issues. The document provides information on pros, cons, and suitable use cases for each cross-platform approach.