Task blocks use the well-known fork-join paradigm for the parallel execution of tasks.
Who invented it in C++? Both Microsoft with its Parallel Patterns Library (PPL) and Intel with its Threading Building Blocks (TBB) were involved in the proposal N4441. Additionally, Intel used its experience with its Cilk Plus library.
The name fork-join is quite easy to explain.
Fork & Join
The simplest approach to explain the fork-join paradigm is through a graph.