Will this panel really produce 600W?

Treat 600W as a peak lab figure, not real-world output. A panel of these dimensions typically produces far less, and output falls further in clouds, shade or off-angle sun. Expect it to trickle-charge or maintain a battery rather than run heavy loads.

What can I charge with this kit?

It is built for 12V batteries: car batteries, boat batteries and similar. With the included clips and car charging cable you can connect it directly, and the controller regulates charging. It is not a wall outlet replacement for AC appliances.

Do I need the charge controller?

Yes, use it. The kit includes a 100A charge controller, which protects a battery from overcharging. Its rating is much higher than one panel needs, but it still does the job of regulating the charge.

Can I use it indoors or through a window?

No. The panel needs direct sunlight to produce power. Glass cuts output heavily, and indoor light is far too weak to charge a battery meaningfully.

One 600W solar panel, a 100A charge controller, a connecting wire, four suction cups, a car charging cable and output clips. You supply the battery and the mounting surface.