Google has several good reasons to create a Web browser of its own, but they don’t include killing off Internet Explorer or Firefox. Microsoft, however, does have reason to worry. Big ones.

There are five reasons why Google is doing this:

1. Google wants a browser where its applications like Gmail, Google Docs, it’s just introduced Google Video will run as quickly as possible. To do this, Google is introducing a new multi-threaded JVM (JavaScript Virtual Machine), V8.
   
2. Google wants a browser that can handle large Web-based applications. To make that happen, Chrome includes better memory garbage collection for both its Web tabs and for its V8 JVM. The net result is a Web browser that takes up a bit more memory when you first run it, but doesn’t have the memory leakage problems that cause other browsers to slow down the longer you run them as they slowly but surely eat up all available memory.
   
3. Google also wants a browser that can run multiple applications at once. As it is, the mainstream browsers are single-threaded, single process programs.
   
4. If you’re going to be running a lot of Google applications, Google knows that you want to be sure that your work is secure. To help with that, Google is sandboxing tabs.
   
5. Google is using WebKit, the Apple/KDE-based open-source Web browser engine. WebKit is also what Google is using for its Android mobile phone system.
   

Read more here: The real reason Google is making Chrome