Google Business Profile
A Google Business Profile is a business's free listing on Google Search and Maps, showing its name, address, opening hours, photos and reviews.
What it means
When someone searches for a local business on Google, the box with the map pin, the opening hours, the phone number and the reviews usually comes from its Business Profile. For many customers it's the first thing they see, before the website.
The business owner should be the owner of the profile. A web designer or agency who helps with it should be added as a manager: they get their own login, can do nearly all the day-to-day work, and can be removed in a few clicks when the job ends. Nobody needs to share a password.
An example
A florist changes her opening hours for the holidays. Her website says one thing, and her Business Profile still says the old hours, so customers turn up to a closed shop. Updating both, in the same sitting, fixes it. Google's "special hours" setting is made for exactly this.
Why it matters for your clients
If a designer sets up the profile in their own account, the business may one day find it doesn't control its own page on Google Maps. Keeping the owner as owner avoids that.