What are countersunk screws used for

Hello, My name is Cherry. I'm YuHuang screw's sales manager, more than 6 years experience in hardware industry Born in 1989. Yuhuang Electronics Technology Co., Ltd. – Manufacturer, supplier and exporter of screws in China. If you’re interested in purchasing screw, Please feel free to contact me. Thank you for watching! Skype: cherrymei700 , Tel : +86-135-28527985 , Email : info@www.yhscrew.com , What’s app: +86-135-28527985