Is this a TV or a commercial display?

It is a commercial signage display. It has no tuner or smart apps, so you feed it from an external media player, PC or set-top box over HDMI.

Yes. LG rates its signage panels for continuous commercial operation, unlike most consumer TVs. Keep it ventilated and avoid static images for long stretches to reduce burn-in risk on LED panels.

What do I need to play content on it?

A source device with HDMI output, such as a media player, mini PC or signage box. The display does not include a built-in player or scheduling software.

Is 50 inches big enough for a store window?

It works well for close and mid-range viewing, like a counter or window display. For large rooms or viewing from far away, a bigger panel is easier to read.

Does it come with a stand or wall mount?

Commercial displays usually ship with a remote and basic accessories but no stand or wall bracket. Plan on a VESA wall mount or a separate floor stand.