What is a citation, and why does NAP consistency matter?
A citation is a mention of your business name, address and phone number on another site, usually a directory, a chamber of commerce page or an industry listing. NAP consistency means those three details are written the same way everywhere. It is a widely used practice in local SEO.
The reasoning is simple. Matching details remove doubt about whether two listings describe one business. Google also says prominence draws on information from across the web, including directories. A mismatched suite number or an old phone line gives that information a reason to disagree with your profile.

