What is the difference between Windows 8 and Windows 10?

Hello, Could someone tell us what the differences between Windows 8 and Windows 10 about the display , fonts and GDI? Because we have developed some web applications, 

so Is there any factor that influence the web applications will be change when the OS is upgrade from Win 8 to Win10 ?

If there is , what is the factor and How to modify application in order to adapt the new OS ?

Thanks.