Concurrent processing has been around since the 1960s. In those formative years, we already had systems that permitted multiple processes to share a single processor. These systems are more clearly defined as pseudo-parallel systems because it only appeared as though multiple processes were being simultaneously executed. To this day, our computers still operate in this manner. The difference between the 1960s and the current day is that our computers can have multiple CPUs, each with multiple cores, which better supports concurrency.
Concurrency and parallelism are often used as interchangeable terms. Concurrency is when multiple processes overlap, although the start and stop times could be different. Parallelism occurs when tasks start, run, and stop at the same time.