Google is a company that has most of the world's population as it's customers. It is the most used search engine, and is worth about $3b due to the money that they make with advertising. Also, the money they make is actually also from thier free operating system Android. Even though it is free, they make money simply from advertising and getting paid by smaller companies to stick thier ads on thier websites.
Thier competition is mainy from other large companies like Apple and Microsoft, simply because it is so large that small companies that do the same thing are simply hidden to most people, or they are so small that they become bankrupt or simply stop developing.
Google chrome is a browser commonly used by people today, and it is very secure as Google even pays you to try and hack into it because they want to know how you did it so they can fix it. The browser also let's you install plugins, that, when used properly, will make the browser even better.