Let's say you have a 2 mbps internet connection. The download speed is roughly 250 kilobytes per second. Now, if you want to download a 100 Megabyte file from website X (which I just made up for the sake of this article) theoretically, it should take you around 7 minutes to download the file at a constant maximum download speed.

However, not all websites can send files at high speeds. Let's say website X can only send a file at a speed of 50 kilobytes per second, without a download manager you most likely won't be able to fully utilize the entire 250 kilobytes per second download speed of your connection. Now that's a waste of time and bandwidth. So instead of 7 minutes, it will take you 35 minutes to download the file.

If you use a download manager, here's what it'll do, it will connect to website X 5 times at the same time. The download manager will divide the file into 5 parts so in this case, each of the 5 connections will download 20 megabytes. So even though the maximum speed website X can give is 50 kilobytes per second, since you have 5 connections to it, you'll be downloading the file at 250 kilobytes per second. As soon as all the 5 parts have been completely downloaded, the download manager will combine these parts to create the final file that you downloaded.

http://www.associatedcontent.com/article/2822262/how_do_internet_download_managers_work.html?cat=15

Very informative piece in my opinion.

Cool stuff