Worst question in IT history. It just a disrespectful in anyway. It's the same as to ask musician, what happens between when you pull the string and hear a sound. You can go up the way to quantum mechanics and ending up an advanced medicine. who needs this..? You need to play instrument, at least how it works it's fine but.. let's stop telling how universe works.. it's not musicians job, same goes to software engineer. If I would know what answer to this question in detail, I would go for network engineer not software engineer.