A better question would probably what they don't do; just going off the wiki page (https://en.wikipedia.org/wiki/IBM) for recent history, they're in health care (imaging), weather, video streaming, cloud services, Red Hat, managed infrastructure (which branched off into a company called Kyndryl, which has 90.000 employees in 115 countries), warfare ("In June 2025, IBM was named by a UN expert report as one of several companies "central to Israel's surveillance apparatus and the ongoing Gaza destruction.""), etc etc etc.

Basically they do a lot, but they're not showy about it.