Simple definition
A CPU core is an execution unit within a processor that runs instructions independently of other cores.
Purpose and use
A physical core has execution resources for processing instructions according to the processor architecture.
How does it work?
SMT can expose several logical processors without turning it into several independent physical cores.
Example and verification
Compare physical cores, logical processors and actual workload parallelism before sizing an application.
Points to watch
Not every core in one processor is necessarily identical, and sequential software does not automatically use them all.
In short
Interpret core count alongside architecture and the software being run.