If you use Google Chrome then on opening up Task Manager you may find multiple instances of chrome.exe running. Please note that this is not a bug or a virus, rather an intentional characteristic of Chrome Browser.
The reason behind this is the Stability principle followed at Google Chrome. Google Chrome is visualized more as a platform for running multiple apps, and for such a platform stability is a very important factor, stability as in – one app not hindering the working of other app.
Lets assume that there is only a single process which runs for Chrome no matter how may tabs you open or what operations you do. Now, if one of tab has hung and you want to kill the process, then that would also affect all others tabs or operations given that there exists only single process. Such a thing is definitely poor from user experience perspective and is also not good for platform scenario.
For any software to act as a platform, it should ensure that all the applications which it allows to run on it should not interfere with each other, where the last thing being is crashing each other. Keeping this in mind, Chrome was designed to start a new process whenever there is a new tab or say any plugin operation.
Infact, Chrome also provides an internal task manager using which the memory can be better handled and operations which are not being effective or taking too much of share can be killed without affecting other stuff. Good, right?