can I charge my iphone 15 using a HP

Charge and connect with the USB-C connector on your iPhone - Apple Support

There are two kinds of USB power:

• Traditional 5 volt power
• USB-C Power Delivery power (a negotiated thing)

Both USB-A and USB-C support 5 volt power, but the supply can be quite limited. A USB 2.0 port only has to offer 500 mA (2.5 watts), and a USB 3.0 port only has to offer 900 mA (4.5 watts). I read somewhere that USB-C cables are supposed to be able to carry 15 watts, but you might only get this much from a power brick – not from a laptop.

Apple says that

"If you have a 20W USB-C power adapter or higher-wattage USB-C power adapter — like the one that came with your Mac laptop — you can use it with your iPhone for faster charging."

I don't think that your iPhone will use much more than 20W if offered more. But that's still a lot more than the 4.5W you can count on from a USB 3.0 port.

Yes, and yes.

Presuming that your HP's USB ports provide sufficient current, of course. If it's an older laptop, it might not, or it might only charge your iPhone very slowly.

Regards.