A quick SEARCH using a search engine such as duckduckgo.com or google.com would answer all those questions.
OneDrive is Microsoft's cloud storage service, which allows you to store your documents, pictures, and other files safely and access them from any device connected to the Internet.
You do NOT have to use it unless you wish to. (I don't and furthermore, won't).
I think that you are using Windows 10?
If you wish to disable it, follow the directions at .
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