The abbreviation ff. is used in citation to refer to a section for which no final page number can usefully be given. If there is only a single section following, f. may be used instead. More properly, it is still used, as originally, to refer to the next page or pages in a citation.

Does FF mean following?

ff. abbreviation. ​written after the number of a page or line to mean 'and the following pages or lines'

What does FF mean in references?

The "ff" is not a section or subpart, but is meant as an abbreviation for "and following".