In no particular order, and off the top of my head:
Win10 uses less RAM and boots faster than Win7. *
Win10 has a built-in "reset the OS" feature that basically does the "clean re-install" process for you, like factory-reset on a phone (Win7 doesn't have this). *
Win10 has a pretty good built-in email client, easily an alternative to Outlook if you don't need full MS Exchange support (it has some Exchange support).
Win10 supports sandboxed apps seamlessly with "classic" desktop apps, which largely fixes Win8's "Metro apps suck" problem.
Win10 has virtual desktop support built in.
Win10 has greatly-improved multi-monitor support, such as showing the taskbar across monitors or not, and controlling which taskbars icons appear on. *
Win10 has significantly improved on the "Aero Snap" feature (snap to corners, move the edge between two apps with one drag, etc.).
Win10 has native USB3 support. *
Win10 has native support for mounting ISO files. *
Win10 supports using a Microsoft account to sign in, so all your PCs get the same OS settings, wallpapers, automatic sign-in to Skype and OneDrive, etc. *
Win10's notification center lets you see alerts that you missed or ignored.
Win10 finally has a decent terminal emulator (conhost.exe) that supports things like line-based select and horizontal resize (with re-flow, where relevant).
Win10 has Cortana, which automatically does stuff like track package shipping numbers and tell you when to leave to get to events in your calendar.
That's far from a complete list, but I didn't consult any lists anybody else put together either. That's all just stuff I actually use. I also omitted everything that has to do with touch, focusing exclusively on stuff useful with a keyboard and mouse. Of course, I also didn't list the negatives (and there are some) but there are definitely many things in Win10 that are "truly better than Windows 7".
* denotes changes that were introduced in Win8.x and are still in Win10.