A SharePoint Feature is a functional component that can be activated and deactivate at various scopes throughout a SharePoint instances, scope of which are defined as
1. Farm level 2. Web Application level 3. Site level 4. Web level
Features have their own receiver architecture, which allow you to trap events such as when a feature is
Installing, Uninstalling, Activated, or Deactivated.
The element types that can be defined by a feature include
menu commands, link commands, page templates, page instances, list definitions, list instances,
event handlers, and workflows.
The two files that are used to define a feature are the feature.xml and manifest file(elements.xml). The feature XML file defines the actual feature and will make SharePoint aware of the installed feature. The manifest file contains details about the feature such as functionality.