Linux is a free, open source and extremely stable OS that is a great alternative to Windows. Mint is a specific version built on Linux, there are dozens upon dozens of versions of Linux but I usually recommend Mint for the most "Windows-like" experience and menus, except it doesn't crash or hog resources.
Mint itself has a few versions and for hardware as old as yours I would recommend the MATE version while it misses a few features, mostly in appearance, it is more lightweight so it will run faster on older tech. It uses a Software Manager which is basically like Win10s "app store", but they were doing it about 10 years ago or so, so finding and installing Linux specific versions of programs is easier than it was 10-20 years ago. Sometimes specific software still requires some work but especially if you're just browsing with it, you'll have no issues.
https://linuxmint.com/
Use this to make an install USB
https://www.fosslinux.com/274/how-to-create-linux-mint-live-usb-drive-on-windows.htm
You can actually run the entire OS off the USB without installing to try it out, when you power off though all changes will be lost unless you make it persistent but that is harder and more advanced. It will be slower than normal running off the USB but it's a good way to see it and play with it first.
Linux is not immune to viruses and attacks but it is more secure, partly because it's not mainstream so there's no payoff for hackers.
All the cool kids use Linux.