iTunes on Windows 10 has a sharing capability that allows one PC on your home network to play music that's available to iTunes on another. Still, as a Windows program, iTunes leaves much to be desired.
iTunes is Apple's program originally designed to sync your Windows PC or Mac with iPods and later other mobile devices. Apple's iDevices used to be like dumb boxes that wouldn't work without iTunes on a computer to sync and organize contacts, playlists, and the like.
You don't really need iTunes for your iPad or iPhone anymore. Apple has made the iPad and the iPhone free-standing devices, ready to connect directly to the iCloud. But if you overlook the fact that iTunes is simply one of the worst Windows applications ever created, it has some good points, too.
iCloud is fine as long as everything you own is from Apple. But just try to sync something outside of the iCloud domain, like songs from iTunes. Back up your songs that originated outside iTunes and you should plan on paying the iTunes Match piper. Apple has built a walled garden. Truth be told, all three of the cloud consumer giants — Apple, Google, and Microsoft — have spent just as much effort building walls as building bridges.
As long as all your iPhone/iPad music, videos, or books reside in (or can be retrieved from) the iTunes Store, you're better off starting and staying with the iCloud. (iCloud is Apple's storage service that can store and sync your iPhone or iPad data over the Internet.) Don't install the Windows 10 iTunes app, and don't even try to understand it. Just follow Apple's instructions to set up iCloud.
Switching your iPad or iPhone over to using iCloud is simple: In the iPad or iPhone Settings app, on the left, tap iCloud. Make sure you have the right account set up (you don't want to hassle with mismatched accounts), on the right at the bottom, tap Storage and Backup. Slide the iCloud Backup setting to On. Then wait — an initial backup can take a couple of hours.
If you have some music, videos, or books on your computer that aren't in iCloud, or if you want to be able to pull your iCloud stuff (especially music) into your PC, the iTunes app is something you have to bear with. Two reasons why you may want iTunes:
iTunes is the easiest way to sideload non-iTunes stuff from your PC onto your iPad. For example, if you've acquired books, movies, or TV shows from someplace other than the iTunes Store, it's easier to use the iTunes Windows app to put them on an iPad.
If you've paid for iTunes Match, running iTunes on your PC is the only way to pull music from iCloud and use it on your PC.