Not sure why everyone is talking about Teams and Zoom in this thread when TeamViewer isn't a collaboration tool so much as a remote connection tool, as sokol11 mentioned above.
For home use, TeamViewer is competing with the likes of LogMeIn, Splashtop, RemotePC, Zoho Assist, ISL Online, Parallels Access, AnyDesk, Remote Utilities, Chrome Remote Desktop.
For businesses, TeamViewer is competing with the likes of DameWare, pcAnywhere, Bomgar, and some of the above home use software's business alternatives. Although personally I'd say it's use is surpassed by that of remote connections via Citrix when it comes to the biggest companies.
TeamViewer has a very notable market share in both retail and business for remote connection software. I'm not here to advertise it by any means, just to clarify as some people seem to be misunderstanding its key purpose.