Sections are used to visually group fields in the editor and to control the section's fields when they are defined as repeatable. This is usable when you have a lot of fields and need to group them logically to avoid clutter.
Sections are not custom fields in their own right. If you need to loop over the contained fields, please see related article below on Liquid access to field definitions
Using - (dash) as a title prefix
If you need a section to appear (visually) as a "sub-section" of another section, prefix the section's title with a "-" (dash). This will indent the section in the editor, so it visually appears as a sub-section.
Using # (hashtag) as a title prefix
In general, sections without any fields will not be displayed in the editor. However, if you need to use the section as a sort of message or headline for users using the editor, prefix the section's title with a "#" (hashtag)
Any prefixes used will not be shown as part of the title in the editor.