What is CPU frequency?

Question

Processors

Good day!
Confused in fundamental terminology, help me figure it out. CPU frequency - maximum number:

1. clock signals received by the CPU from the clock generator per unit of time;
   
2. instructions executed by the CPU per unit of time.
   

UPD. Still, the first was confirmed, as I thought. The second is performance in MIPS.

Answer 1

I am for the First Wang.