Switch the portal on per customer (their record → Customer portal) and they can sign in with a secure email link — no password — to see their upcoming visits, past work with photos, quotes, invoices (payable online), messages and recommendations. They only ever see their own data, and you can hide financials for sites billed centrally.
Not sure what you're sharing? 👁 Portal preview (linked from the customer's portal card, or Business → Portal preview) renders their portal exactly as they'd see it — great for demos and for checking before you switch someone on.