Using generic terms and not nitpicking on details:
Concurrency is when the system does different things at the same time, which can create race conditions, transactional problems, etc. People generally have conceptual problems with it because it requires a higher level mental model.
Parallelism is when the system does the same thing, multiple times, at the same time. This is very easy to understand, conceptually: Have that list, run that same function for each list item in its own thread, then we get the results in a new list at the end. But its very hard to do well at low level, when we are talking compilers, hardware, etc. (And I know nothing about it but I know it’s a field of the discipline). But at a higher level the word totally applies: Got this advent of code problem, it’s slow, let’s use Task.async_stream 
And of course parallelism implies concurrency.
Nice article. I wish I knew a way to dump in the console whenever data copied from one process to another is more than N bytes.
