What is the difference between Guest and Incognito modes of Chrome browser?

They are more or less the same, but for different situations.

I'm going to assume you've read the relevant help pages for guest and incognito modes

Incognito mode is designed to be used alongside your regular profile on your own PC. It has access to your bookmarks and other profile information.

"Guest" is a profile on its own designed to be used to be used on a PC you don't control. It is seperate from any existing profiles.

The big difference is that your incognito window has the information from your current profile, and just dosen't save what you do in that window. Guest mode both restricts off information from other profiles and wipes anything you do.