I wonder How do Google make money from "Google Chrome Web Browser", because it is an open source and free to download.. How do they make profit from it..

Google's primary source of revenue is from advertising. Everything else they do feeds into this, directly, as in gmail, or indirectly, as in android and chrome. Chrome mainly provides market penetration. People are more likely to use google tools, such as gmail, calendar etc, if they play well with other google tools, such as chrome and android.

what about Mozilla Firefox

Can I point out that they don't have to? Given the wealth of the Google corporation, they can afford a few (well, actually quite a lot of) projects on which they don't directly make any money.

On the other hand, if you were a Google exec, one of the things that must have given you nightmares was the idea of one of your competitors creating something that pushed people away from your biggest cash earner. So, say, there were another browser supplier who had their own search engine, there was always a risk of them manipulating their browser in some way to make your main product harder/less convenient to use and that this might threaten the future existence of the corporation.

If you can make a better browser, and people move over to that better browser, then that risk is diminished.

For a while now, Firefox has had a search box in the top right hand corner. The default search provider for this box is google. Google pay handsomely for this feature.

Many of the large open source projects have the backing of big players in the industry. Red Hat is one of the biggest kernel contributors in both code and cash, as are IBM, Intel and so on. Google is also one of the biggest sponsors of projects in terms of cash.

Many open source projects sink or swim not in the direct profitability of the products they create, but on the support of large business that benefits from the use of these products.