This document compares JavaScript libraries JQuery, Mootools, and Rialto. JQuery is the smallest at 16-94KB and supports back button navigation and rich text editing. Mootools is similar in size at 4-74KB but lacks back button support and rich text editing. Rialto is the largest at 520KB and does not support back button navigation, rich text editing, or animation. The document also notes advantages of these libraries are their extensibility and ability to quickly build interactive applications, while a disadvantage is potential browser compatibility issues.