How is Sencha different from Ext JS?

While Ext JS is a framework for building client side apps for desktop, Sencha Touch is basically a framework for building client side adds for mobile devices. One could easily compare Ext JS to Sencha Touch in a similar way as comparing Windows to Microsoft. Obviously, modern browsers on desktop, pads or phones should support Ext JS framework. However, Sencha Touch is optimized for the pads and phones. Since maximum numbers of people are known to access the mobile and web apps with their mobile devices, Sencha Touch is an important tool for all developers.