Why does Chrome has so many processes running, when I have just opened the application? [duplicate]

That's Chrome's sandbox in action.

Chrome runs some of its components as separate processes. There's one main process, a GPU renderer process and then (roughly) a single process for every tab, extension and plugin. (Actually, a few tabs can be run in a single process under certain circumstances.)

It's how Chrome's sandbox works. Sandboxing is a technique used to increase program's immunity against malicious actions of untrusted code (such as code of websites you're visiting). Running independent pieces of code in separate processes makes these pieces of code unable to affect Chrome's core, which is the most privileged part.

Extra processes don't necessarily use that much resources. Some of the memory is shared between them and dormant processes use negligible amount of CPU time. Nothing to worry about here.