What it means
A proof point is something a stranger could verify: family run since 2008, open seven days, 312 five star reviews, gluten free kitchen, city and guilds qualified. Best in town is not one, because there is nothing to check.
Why it matters to a small business
Specific and checkable outperforms superlative and vague, and it also keeps you out of trouble. A list of proof points written down once becomes the raw material for every post, every ad and every page, and it means the person or tool writing your copy has facts to reach for instead of adjectives to invent.
The bit people get wrong
Proof points go stale quietly and that is when they become a false claim. Since 2008 stops being interesting and starts being a maintenance job. A review count you quoted last year is wrong now. Put a date against each one and check them when you check anything else.