What it is
Before someone calls a business they have never used, they read its reviews. Google does the same thing in its own way: the number of reviews you have, how recent they are and how you answer them all help decide who shows up in the map results. A business with 11 reviews next to one with 170 is at a disadvantage before anyone has seen its website.
Most businesses have plenty of happy customers and very few reviews, for a simple reason: nobody asked, or the customer meant to and forgot. Review management closes that gap. After a job or a visit, your customer gets a short, friendly request by email or text with a link that opens the review box directly. If they don't get to it, they get a reminder.
Every customer is asked the same way. I don't filter out the unhappy ones, which Google's rules forbid; you hear from them too, and you get the chance to put it right and to answer in public.