A donor is the person or organisation behind the gifts: a register entry with a code (DNR-…), a name, a type — individual or organization — and the contact details the relationship needs, including the tax ID their receipts and year-end statements are issued against.
A donor is not a customer. Nothing is owed, no credit is checked and no receivable is ever raised: the relationship is the giving history, read through Donations by Donor (§12.9). Donors are created as gifts arrive — including from the donation form itself — and a donor made inactive leaves the pickers while their history stays exactly where it was.
The donor's own page is the Donor 360. Opening a donor shows three tabs beside their details. Donations lists every gift they have made, newest first, each amount in the currency the gift was actually given in. Campaigns lists the campaigns this donor has given to — the campaign recorded on each gift when it was entered — with their gift count, their giving in functional currency, and their first and most recent gift to each. Activity is the shared timeline: their gifts, your team's notes (pin one, set a follow-up, @mention a colleague), and the record's own change history, in one stream. A campaign's page carries the same Activity tab — its gifts, notes and changes together.