They are language agnostic generic concepts. Concurrency deals with dependency, or the lack of, among tasks and their running order. Task A must run after tas

They are language agnostic generic concepts. Concurrency deals with dependency, or the lack of, among tasks and their running order. Task A must run after task B, B after C, etc. A, B, and C are not concurrent tasks. D can run at anytime. D can run before, after, or at the same time of A/B/C. The ordering doesn't matter. In this case D is concurrent to A/B/C. The concurrent tasks MIGHT run at the same time but it's not necessary. It's up to the OS/system scheduler. Concurrent tasks can run on a single core cpu serially and they are still concurrent tasks. Parallelism has to do with efficiently cranking as many tasks as possible to actually run in parallel. E.g. given 10 cpu, how do I fully utilize all the cpu at the same time? Mostly it has to do with data partition to make sure the cpu can get evenly distributed non-depending data. Concurrency and parallelism can be mixed at the same time. E.g. in the map-reduce pattern, the map part utilizes parallelism to distribute the data to process at all the cpu. The reduce task has dependency on the mpa tasks; running order means concurrency is in play there.