The document introduces Salesforce Lightning and its key capabilities for admins:
1) The Lightning Experience provides a modern, efficient user interface for desktop, tablet and mobile that resembles consumer apps.
2) Lightning Connect allows connecting to external data sources through the OData standard and accessing the data as if it were custom objects.
3) Lightning Process Builder visually designs business processes by connecting different steps without code through a point-and-click interface.
4) The Lightning Design System provides common UI elements, templates and best practices to customize the look and behavior of applications consistently.