The internal sentence. Not the homepage. Not the tagline.
A positioning statement is one to three sentences that record who you serve, which category you compete in, what makes you different, and why that is believable. Teams use Geoffrey Moore’s formula. It stays internal until you rewrite a clause for the site.
A tagline is public and short. A positioning statement is internal and complete. If you publish the full statement as a headline, you are asking a stranger to read a strategy memo.
30–60 words. Longer means you have not synthesized.