A client portal is a private section of a website or system where each customer sees only their own information. Typical contents include job progress, quotes to approve, documents to download, invoices and a way to send messages. Each customer logs in with their own details and sees only what has been shared with them.
It saves time on both sides. Customers stop phoning to ask where things are, and staff stop emailing attachments back and forth. Because everyone sees the same record, there is less confusion about what was agreed. Good portals control access carefully so that one customer can never see another's details.