This article does not apply to Umbraco 8.
The concepts and code in this article have been deprecated in Umbraco 8 and no longer apply.
If you are using Umbraco 7, this article is perfect for you!
SectionService
The Umbraco backoffice consists of Sections, also referred to as Applications.
In previous versions the SectionService was used to control/query the storage for section registrations in the ~/Config/applications.config file. This config file no longer exists in the current version and therefore the SectionService has become unnecessary.