The initialism FAQ (Frequently Asked Questions) falls into the same category as initialisms such as PDF, URL, HTML etc.

Just as we don't spell out Portable Document Format or Hypertext Markup Language each time we use the terms, the term FAQ is widely recognised and doesn't need to be spelled out in full.

You don't always have to use the initialism, of course. However, if you're using the full meaning as a phrase, lowercase it.

For example:

The Authority has a number of FAQs online.

.. or ..

You can read the answers to frequently asked questions about apprenticeships.

If you need to write FAQ as a plural, use FAQs - not FAQ's. FAQ's is possessive.

It's Written - Now What? FAQ Organisation and Structure