There's a "light" version available online, but you must be thinking about Office 365.
Although the core product is still desktop based, they've been shifting to an optional subscription model where you pay $9/month or so for perpetual updates and 1tb of storage.
This model is great for me. It's very rare that I need to view or edit a document in an Office application but it does happen occasionally when the formatting is complex or something. Just install Office in a VM, pay $9 for 1 month of access, and unsub again when I'm done!
Although the core product is still desktop based, they've been shifting to an optional subscription model where you pay $9/month or so for perpetual updates and 1tb of storage.