What impact do queries have on a server's resources?
A query takes some combination of CPU and I/O.  It might be 100% and 0% if everything it needs is cached in RAM, or it might be 1% and 99% if nothing is cached.  Or anywhere in between.

Only one "core" of the CPU will be used for one connection in MySQL.  Multiple connections could use all the cores; but I rarely see that.

Another issue is "locks" or "mutexes".  This is where one connection is busy doing something, but has a lock on something; and another connection wants that something.  Now the second connection has to wait, not using CPU or I/O.

So, 0.1 seconds (or a full minute) does not really say anything other than that the user had to wait that long for the answer.  It will be some combination of CPU (one core), I/O, and being blocked.

The Operating system is responsible for parceling out resources such that the system never appears to be "locked up", and everything gets done eventually.

I have seen a query take 57 hours; it was mostly I/O.  I have seen queries that I could estimate would take months.  And I have seen queries that take far less than 0.1 second.

And I have seen systems that are running over a 1000 queries per second even though every query took more than 1/1000th second.  This is the magic of Operating systems.