GCD vs. Operations Section1 chapter2 Do not understand

“In other words, a task being synchronous or not speaks to the source of the task. Being serial or concurrent speaks to the destination of the task.”
What does this sentence mean? Can you express this sentence in another way?

hi! I just saw this post today. Those sentences are a shorter version of what I say in the video course:

You can run a task asynchronously or synchronously from a serial or concurrent queue, on a different serial or concurrent queue.

Synchronous vs asynchronous tells you whether the current queue has to wait for the task to complete. Serial vs concurrent just tells you whether a queue has one or many threads, that is, whether it can run only one or many tasks simultaneously.

Synchronous vs asynchronous is about the source of the task. Serial vs concurrent is about the destination of the task.