When I’m shopping for a desktop computer, I hear two numbers constantly: Clock speed (usually in GHz) and core/thread count. What else is there to CPU performance besides these two numbers? What makes a modern CPU more performant than a CPU from years ago, assuming the same core count and clock speed?
Other people answered how it’s measured, but if you’re just shopping for a CPU I’d recommend skipping straight to benchmarks. There’s a lot of technical stuff involved but if you look at Geekbench/Passmark scores you can easily compare which ones are more powerful.
If you’re shopping for a laptop with a specific CPU I’d also look into how much power it uses (in Watts).