A review link is a short web address, generated by Google for your business, that opens the review form straight away with the star rating on screen. The customer taps it once and writes. No searching, no scrolling, no finding you among three competitors.
Where to get yours
It comes from your own Google Business Profile. Sign in at business.google.com, open your profile and look for the option to ask for reviews or get your review link. Google makes a short link for your business and it does not change, so copy it once and keep it.
If the layout has moved since you last looked, the current instructions are on Google Business Profile Help.
Where to put it
Save it as a text shortcut on your phone, because the text you send from the van is what actually gets reviews written. Put it on the thank you page people see after sending an enquiry. Put it in your email signature and on the bottom of your invoices.
One place it should not go is a printed card handed to every passer by. Reviews from people you did not work for are the sort that get removed.
A worked example
A paving firm finishes a drive in Ossett, walks the customer round it, and asks out loud while they are both looking at the block work. The customer says yes. The link goes over by text before the van moves.
That is a review written that evening, naming the job and the town, which is the exact wording the next Ossett customer will be searching for. Asked a fortnight later by email, the same job gets nothing.