Orders are the rows of the Orders grid, one row an order, for orders placed in the last 60 days.
Permission
The first press of Edit orders asks Shopify whether the app may read your orders. A store where Shopify has not yet approved the app to read orders sees "Orders are not available yet", with nothing to press.
Shopify's own fields
Note, Tags and PO number. An order's customer, addresses and line items are not edited here.
Your metafields
Every order metafield definition of a type the app edits, by name. See Which fields can be edited.
Finding orders
Search by the order's number, with or without the #. Filter by Payment status, Fulfillment status, or Date placed: today, the last 7 days, the last 30 days. An order older than 60 days is not listed.
In a file
The CSV file of orders holds Order ID, Order, then your fields. A row whose order is older than 60 days is skipped: "No order from the last 60 days has this ID."