In parallelism, processes 1 and 2 are able to execute at the same time and also operate completely independent of each other. This means that the steps involved in the concurrency example might end up delaying each other in some way (for example, if Task B is ready to begin right as Task A completes and is spitting back output).
We will talk in much greater detail about this, but the model behind Elixir makes it so that parallelism is the default state every time and is handled extremely efficiently. Also, you may notice that the definitions for concurrency and parallelism overlap each other a little bit; something that is concurrent is not necessarily parallel, but something that is parallel is ...
