Will it charge an iPhone at 15W?

No. The pad is rated up to 15W, but iPhones draw their own Qi wattage, which is lower. Expect standard Qi speeds on iPhone, and check your phone's wireless charging spec for what it accepts.

Do I need my own charging cable?

A Type-C cable is included. You still need a USB power adapter or a port that supplies enough power, and some computer and laptop USB ports may not be enough to charge a device through the pad.

Does it work with a phone case on?

Qi charging generally passes through thin cases. Thick, metal or wallet-style cases can block it, so remove those before placing the phone on the pad.

Can I plug it into my laptop's USB port?

It may not charge reliably. The manufacturer notes that some computer and laptop USB ports do not supply enough power to charge a device through this pad. A wall adapter is the safer source.

How do I know it is charging?

The multi-color LED edge lights and the white center light come on when the pad is in use. If nothing lights up, the phone is likely misaligned or the power source is too weak.