When two visitors click a web form submit button at the same time which data go to the server at first?

In different websites, there are a lot of forms. Each form contains a submit button. By placing information in the fields we click the submit button. If more than one persons click a submit button at the same time from different computers, then which person's data go to the server at first? And on the internet/network which mechanism is following to store the data?? In my website, I am using core java language and MySQL database.