Content blocks make up the different 'sections' of your web pages. Every area is broken down in to different blocks - making it nice and easy to drag different sections around and add new parts to a page.
The best way to edit your website is normally using 'Canvas Mode'. It allows you to look at a live preview of your website and edit it there and then in a similar way you would a Word Document or something similar.
Canvas Mode is mainly for design changes to your website and editing content on the page. It's not the place to make technical changes or change any e-commerce pricing - that's all best in the Admin Area.