What it means
NAP stands for name, address and phone. Consistency means the version on your website matches the version on your Google listing, which matches the version on Facebook, the directories, and the old listing somebody set up in 2019. Search engines and assistants use those matches to decide they are all the same business.
Why it matters to a small business
It is the plumbing under local search, and small businesses break it without noticing, usually by changing a phone number or moving premises and updating four places out of nine. The old number keeps ringing somewhere for years. Marketeer's own AI visibility check reads the phone numbers your site publishes and flags it when the same page shows two different ones.
The bit people get wrong
The formatting matters less than people think and the digits matter more. 01227 555010 and +44 1227 555010 are recognisably the same number. 01227 555010 and 01227 555011 are not, and one of them is a number you stopped answering in 2021.