Take a look at the Jaeger and Zipkin websites and it should be pretty clear what it is used for.
The point of OpenTelemitry is to make it so you could write the places you get your traces/metrics in one part of code and configure which backend system it is collected into in another part.
So, for example, you'd add a `trace("my slow thing"){ be slow }` into your code and later add `report to zipkin` or `report to Jaeger` in another part. The place where you trace "my slow thing" doesn't care about how to interact with the backend system or which backend vendor is ultimately used. You can start using prometheus, zipkin, new relic, Jaeger, whatever, just so long as they have an OpenTelemetry adapter you are golden.
The analog is SLF4J in Java.
It's baffling to me, what do people think happens when they pull/push from a GitHub repo?
GitHub ≠ Git. Far from it.