With all the stuff about chips and fabs and Taiwan in the news in the past year, you'd have to be living under a rock to not know who TSMC and ASML are.
However, I too have never heard of KLA. Somehow it never gets mentioned alongside those other companies. Maybe it's similar to how everyone knows about Microsoft and Apple, and even my mother knows what Linux is, but almost no one has heard of Green Hills Software?
KLA, ASML, TSMC are companies that are huge globally in their fields.
The field being semiconductor design and fabrication.
Whatever device you're reading this on almost certainly has components made with machinery by one (or all) of those.