org-category

org-category is a variable defined in `org.el'.
Its value is

nil

• Automatically becomes buffer-local when set.
• This variable is safe as a file local variable if its value
  satisfies the predicate which is a byte-compiled expression.
  

Documentation:
Variable used by org files to set a category for agenda display.
Such files should use a file variable to set it, for example

# -*- mode: org; org-category: "ELisp"

or contain a special line

#+CATEGORY: ELisp

If the file does not specify a category, then file's base name
is used instead.