PNGs support either 24-bit or 8-bit colors. The higher the bit support, the more available colors there are for that PNG — and the larger the file size. If your website has a simple logo that is a 24-bit PNG, that file is taking up unnecessary space and slowing down your page load time. Converting that image to an 8-bit palette will reduce the file size without affecting its visible quality. Now you have a smaller file taking up less space in storage and your page will load slightly faster.