Is there a difference between concurrency and paralleism. if there is how are they in common, and how do they differ?

There are differences between concurrency and parallelism. They are in common about how and in which frequency  the tasks are being performed and how many tasks can be performed.

Explanation:

Concurrency refers to fulfillment of a large number of tasks that are not completed in any particular order during the beginning, running and overlapping periods. When we talk about at least two or more tasks, concurrency is inherently applicable.

The parallelism does not require the existence of two tasks. In the true sense of this word, each task or subcontractor performs part or all of the tasks using the CPU's multifaceted infrastructure by identifying one nucleus for each task. Parallelism requires hardware with multiple processing units. You can get compatibility on a single-core CPU, but no parallel.

Now let us list the notable differences between concurrency and parallelism.

1) Concurrency is the time when two tasks can begin, work and complete in overlapping periods. Parallelism is the simultaneous implementation of tasks, for example, at the same time. in a multi-core processor.

2) Concurrency is an independent process, and parallelism is the simultaneous (possibly related) performance of calculations.

3) Concurrency is to deal with more than one thing. The parallel is to do more than one.