Sections and blocks are pre-designed building blocks to help you create and design your website. Both will automatically adapt to fit the style and design of your template, and of course, you can edit them as much as you want.
A section is a slice of your website consisting of several components grouped together around a theme such as contact, welcome, and about. When you drag a section into your workspace, it will make room for itself by moving existing content up or down, without breaking your layout. A section will always cover the entire width of your site and cannot overlap another section.
A block is a container with text - and possibly an image - styled around a theme like lists and reviews. You can add a block to a section of your site.
You can find sections in the component menu to the left of your screen. Blocks are available under text and contact.