Does it come with a battery and charger?

The PSD101B is the bare tool; the PSK005 kit pairs it with a 2.0Ah 18V battery. Check which version you are buying, since the bare tool needs a One+ battery and charger you already own.

Will my other Ryobi One+ batteries work in it?

Yes. It uses the standard One+ 18V battery, so existing One+ packs fit. Larger packs add runtime but also weight.

How long does it run on a 2.0Ah battery?

Expect short sessions rather than long continuous sanding. A 2.0Ah pack gives light-duty runtime, and heavier work drains it quickly; a larger pack extends it.

What size belts does it take?

It uses standard 3-inch by 18-inch sanding belts. Buy a few grits, since the tool is best for light stock removal and finishing rather than heavy material removal.

Is it good for stripping paint or sanding floors?

No. It is a light-duty cordless sander. For large surfaces, paint stripping or floor work, a corded belt sander with more power and runtime is the better choice.

How does it compare with a corded belt sander?

It trades power and continuous runtime for cordless convenience. It is fine for touch-ups and small jobs, but a corded sander removes material faster and runs as long as you need.