Let us say one we have 5 steps in our thread group and we add 20 users to our thread.When we run our thread 20 users will send request one to the server and will get a response back in time.The first user who will get a response back will go to the next request.

Like for example if first step in homepage. When one of the users got the response from the homepage request it will go to the next step without waiting for other users.

But what if we want that no user should go to next request until at least 15 users have got response for their first request.

So we use synchronization timer in that case. We set that wait for at least 15 users to come back from homepage before we go to scenario page.

So we add a sybchronization timer and put "Number of simulated users to group by" = 15

Let us say 14 users come back fast but user 15 is very slow and taking lots of time then we can even settime out to 10 secs i.e maximum users to come back is 15 ,but wait period is 10 secs so if all 15 users don’t come back in 150secs don’t waste time go to next step instead.