The asynchronous ad code is a fully asynchronous version of the AdSense ad code that offers improved web latency and a better user experience for your site’s visitors.
here is the briefly description regarding to your question.
When you execute something synchronously, you wait for it to finish
before moving on to another task. When you execute something
asynchronously, you can move on to another task before it finishes.
That being, said, in the context of computers this translates into
executing a process or task on another “thread.” A thread is a series
of commands–a block of code–that exists as a unit of work. The
operating system can manage multiple threads and assign a thread a
piece (“slice”) of processor time before switching to another thread
to give it a turn to do some work. At its core (pardon the pun), a
processor can simply execute a command–it has no concept of doing two
things at one time. The operating system simulates this by allocating
slices of time to different threads.
Now, if you introduce multiple cores/processors into the mix, then
things CAN actually happen at the same time. The operating system can
allocate time to one thread on the first processor, then allocate the
same block of time to another thread on a different processor.
All of this is about allowing the operating system to manage the
completion of your task while you can go on in your code and do other
things. Asynchronous programming is a complicated topic because of the
semantics of how things tie together when you can do them at the same
time. There are numerous articles and books on the subject; have a
need further please let me know. Till Then stay mast stay cool…