I purchased a new laptop with Windows 10. As part of the intro it asks if you would like to use OneDrive. Even though it will only be myself and my wife using it, I decided to give it a try. Until now if I wanted to share something between our computers I would use a USB stick to transfer a file or folder. Now with OneDrive, I'm wondering if I'm correct in thinking that this could be used to do exactly that - i.e. transfer files or folders from one PC to another.
From what I read, you can set options in OneDrive to be available only to the two of us, so it should be secure.
Does using OneDrive for this purpose make sense?
Yes. And that is kind of primary purpose. OneDrive (like Dropbox, Google Drive, and Box) is an online storage service that offer "syncing". What this means is that you have your local copy that is then synced to the Microsoft servers and then can be synced to other computers logged into your OneDrive account. So, in effect, when you save a new file to the OneDrive sync folder(s) or edit a file or delete a file, those changes will get "uploaded" (which too crude of a way to say as it is more than just an upload) to the OneDrive server. Then once any other computer that is signed into that OneDrive account connects to the OneDrive server, it will "download" those changes to those other computers. The result is that what is on and happens on one computer using the OneDrive account will happen to the others.
Now, this will not happen to everything on the computer. Typically for such a service, there is a specific folder where you say any files you want synced to OneDrive. You can create subfolders within that folder, but it will typically ONLY sync/upload stuff from specific folder (or any subfolder inside it). I don't actively use OneDrive (I get a lot of OneDrive storage with my Office 365 subscription), so I cannot say it 100% works this way, but I do know that both Box and Dropbox do and they are both rather similar in nature to OneDrive.
Also, I suppose you can use OneDrive as a handy way to perform regular backup of files and folders?
Yes, in a way. Again, it will likely only upload (aka "backup") files and folders saved in that one specific folder on the computer. But, what you put there will be "backed up" to the OneDrive servers and also be "backed up" to any other computer using the OneDrive account.
Now, keep in mind that it will not protect against all things. It will help protect if one computer or its drive dies. OTOH, if you delete a file or a file gets corrupted or infected, then it will not really help there. The exception is that I believe that OneDrive offers versioning for at least some file types (i.e. Microsoft Office file types at a minimum, I believe). Versioning means that the servers will save multiple versions of that file as you make changes to it. So, if a file gets corrupted or infected or you delete, you might be able to recover a previous version of that file from the OneDrive web interface.
Overall, it is not meant to be "true" online backup service. There are other services that offer that ability like CrashPlan or iDrive. But, it can provide some backup ability.