Settings → Business values holds values that belong to the business rather than one contact: a review link, a booking link, opening hours, an offer code.
Each value has a Name, a Value and a key fixed when it's made, such as review_link. Copy tag copies {{business.review_link}} to paste into an email, a task or a note. Renaming a value doesn't change its key, so emails keep working.
Change the value once and every email and automation uses the new one from then on. An automation can change a value too (Update a business value). Deleting a value leaves an empty space in emails that use it.
The built-in Review request template adds a Review link value for you to fill in.