Page layouts control the layout and organization of fields, sections, related lists, buttons per object. They also help determine which fields are visible, read-only and required. The page layout editor helps you organize pages with custom links by a simple « drag and drop » action.
You can also add a report chart to a page layout.
One page layout per profile. You can drag up to 20 s-controls, 20 Visualforce pages, 20 expanded lookups, and 100 related lists onto a page layout. There are no limits on fields and custom links.
Salesforce recommends creating NO more than 200 page layouts. While there is no limit, organizations may have difficulty managing their page layouts if they exceed 200.