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.
Moving a visit and querying an invoice. Every upcoming visit in the portal has Need a different date? — the customer picks a preferred date (today onwards) and morning/afternoon/any time, adds a note, and it lands in your Portal requests as a date change. Their visit stays where it is until you press Move visit & notify on that request, which moves it, tells the assigned crew and emails the customer the confirmed date; meanwhile the portal shows "Date change requested" on that visit. On their Invoices page each invoice has Query this invoice, which opens Messages with the invoice number already typed, so the question reaches your Inbox saying which invoice it's about.