what is new in windows 10?

What's new in 1703 is detailed in links below

https://docs.microsoft.com/en-us/windows/uwp/whats-new/windows-10-version-1703

https://docs.microsoft.com/en-us/windows/whats-new/whats-new-windows-10-version-1703

Do you mean Creators Update?

You can start here: https://www.microsoft.com/en-US/windows/features