I have been using this for years for my wife to backup and sync her school files between her school computer and her home computer. It is free and easy and will do exactly what you want.
You did not say which computer system you use but this is for windows.
https://www.microsoft.com/en-us/download/details.aspx?id=15155
Windows 8.1, I'll give this a try thank you Don
I use Acronis True Image..
that is not a incremental backup though. That is a Full Disk-Image Backup. Basically good for a full restore only and not just for a few files. Good to have one and I do that every day also but sometimes you just want to restore a few files.
Bought and downloading nowCarbon Copy Cloner on a Mac...