What does the Source filter on my order list mean?

Source is where the order was created. The same value appears as the Order From column on Orders → Manage Orders and in the Order From box on each order.

• Website: placed by a shopper on your online store.
• Mobile App: placed in your store's mobile app.
• POS: rung up at your shop counter on the POS.
• Admin: created by you or your staff in the admin. This includes manual orders, CSV imports and quotes converted to orders.
• Vendor Backend: created by a vendor in their own panel (multi-vendor stores).

Open the filters panel, pick a Source, and the list shows only those orders. The choice appears as a chip you can clear with ×. Older orders saved as "storefront" or "vendor-backend" are included in Website and Vendor Backend.