This presentation was given on Thursday, April 14, 2016 which was more than 18 months ago , this means the content may be out of date or no longer relevant. You should verify that the technical information in this presentation is still current before relying upon it for your own purposes.
LessCSS extends the CSS language to make it actually useable by adding features like variables, mixins, functions, and a bunch of other techniques that allow you to make your stylesheets more maintainable, themeable, and extendible.