Frankly, I don't believe I've ever used them so I can't comment on how similar or dissimilar they are from the full desktop versions. The online versions are cleverly named Word Online, Excel Online, etc. Microsoft offers a web-based version of these applications.The online versions are only available if you have an Microsoft 365 subscription. It is important to know that regardless of whether you buy Office as a stand-alone product or as part of Microsoft 365, you get the ability to download and install Word, Excel, PowerPoint, etc on your Mac. I'd like to point out a few other considerations that I think you should keep in mind as you make your decision. Are you trying to decide if you should buy Office for Mac as part of a Microsoft 365 subscription or as a stand-alone product? While cost is one important consideration it is not the only one.