While a microprocessor is a physical implementation of a logic design, an IP core is the design (or the layout) itself. Therefore, it is also possible to see an IP core as the “core” of a microprocessor and as such calling it “microprocessor core”.

Commercially, the term core (or microprocessor core) is used to refer to the number of similar logic design (or layout) replicated inside a single microprocessor: Therefore, a dual-core processor will have two similar design duplicated in a microprocessor and a quad-core processor will have four similar design replicated.

Typically, the number of cores you have in a microprocessor will be a factor on deciding the number of threads (applications) that you can run on a computer at the same time (in parallel).