As you know, you can store your data in the cloud like Dropbox, Mega and OneDrive, etc. However there are other free solutions. If you have two or more computers in your house, you can store your backup on the other computer by opening a share between them.
There is software like Syncthing (free) which can copy your data to another computer aywhere in the world, or into space assuming you have internet there. That data can be encrypted too if you wish. Syncthing is free and works on multiple platforms. I have win7 and Win10 and my Android Cell sharing data. Some of the data between the windows systems is bi-directional menaing I have the same data on each system. The cellphone just sends photos to my Windows systems.