Why does it say if I turn off my iCloud backup ( only because I am noticing less of my documents in my ICloud) that the next backup will begin through my iTunes through my computer when I don’t own a computer

? ( Only because I am noticing strange things going on with my ICloud and other things that are connected to my phone I didn’t know about ) Why is it saying if I turn off my iCloud backup then my next backup will be through my iTunes through my computer which I do not even own a computer nor is there one in my home .