Microsoft is introducing ads into a free version of Office, which seemingly only lets users save to OneDrive.
In other news, LibreOffice is also free, doesn't have ads, and lets you save your documents wherever you want. I use it every day for my work. It is available here:
@neil
I use Open Office, and I have been relatively happy with it, over the last 15 years. It can save as and open Office files (including Excel).
@Darkphoenix You might want to read this, as OpenOffice has multiple unfixed security issues over a year old, so it's risky to stay with it: https://en.wikipedia.org/wiki/Apache_OpenOffice#Security