Custom Layouts / Ext JS 5, Touch
The Layout system is one of the most powerful and unique parts of the Sencha frameworks. Layouts handle the sizing and positioning of every Component in your application, so you don't need to manage those pieces manually. Ext JS and Sencha Touch have many similarities between their Layout classes, but most Ext JS and Sencha Touch developers have probably never looked under the hood of the Layout system.
This video compliments the blog post seen here: