What is the difference between this and a direct thermal printer?

This model uses a ribbon, so the print is fused onto the label and resists heat, sunlight and rubbing. Direct thermal printers need no ribbon but their labels fade over time and in hot conditions.

Can it print wirelessly?

No. The TD-4420TN connects by USB only, so it needs a computer or USB host nearby. For network or wireless printing, look at Brother's networked TD models.

What label sizes does it take?

It accepts roll labels up to about 4.4 inches wide, which covers standard shipping, barcode and shelf labels. Check the media specifications for the exact roll and core sizes supported.

Do I need to buy ribbons as well as labels?

Yes. Thermal transfer printing uses a ribbon along with the label roll, so budget for both. Using the correct ribbon and label pairing matters for print quality and durability.

Can it print without being connected to a computer?

No. It has no keyboard, display or standalone mode, so jobs are sent from a connected PC. That is typical of desktop label printers at this level.

Is it suitable for high-volume warehouse printing?

It is a desktop unit aimed at light to moderate duty. Very busy warehouses printing thousands of labels a day should consider an industrial printer with heavier duty cycles.