Osnap mode is more for taking screenshots of webpages, while Ortho mode is more for taking screenshots of the desktop. Osnap mode is a tool that is built into Windows 10. It allows you to take screenshots of webpages by pressing the "Print Screen" button on your keyboard and then pasting the screenshot into an image editing software like Photoshop or Paint.
Ortho mode is a tool that can be found in Windows 10's Snipping Tool. It allows you to take screenshots of desktop by pressing the "Print Screen" button on your keyboard and then pasting the screenshot into an image editing software like Photoshop or Paint.