I always have a mixed fillings about section structure in Revit. Therefore I decided to explain it in details.
1. Each section definition consists off Callout Tag (used for Detail Section or View Callout) and Section Tag.
2. Section has three ways of ending: Section Head (1) Section Tail (2) or none (3). To change look of ending, just click on two circular arrows.
3. After going deeper into Section Tag family you can personalize its look.
4. Section Head and Tail can be found under Families > Annotation Symbols > Section Head or Tail.
5. New symbol family should have a different name and be loaded into a project so it can be used as Section Head or Tail value.
There are 2 parameters you can set for the symbol: the Drawing Number and the Sheet Number. You can set them by placing Tag Text. The Drawing Number is the number of the view on a sheet. The Sheet Number is the number of the drawing sheet. If you add these parameters to a symbol, they automatically fill in when you add the section view to a project.