The design of the CPU is the main part of it and how that design works with other components, the operating system and the software that is run on the processor.
IPC is also a part of determining CPU performance, this is how much work a core can do in every clock cycle (1 Hz), this is where intel has an advantage since their cores are able to achieve more work per cycle because of how the architecture is designed.
There is a lot more that is involved but it can become a bit confusing after a while.
You can find a lot of sources on what makes a CPU what it is and what can affect its performance if you are interested.
Don't know if that helped and doesn't bother me, its what we are here for.