Apple's Activity Monitor allows you to view all the running processes (system-based or user-initiated) on your computer to see which are using the most resources. After installing Google's Chrome browser, you may find that Activity Monitor can get filled with Chrome-related processes.
This happens because unlike Safari and Firefox, which run in a single process, Google Chrome is built so the view for each window is run in a separate process, allowing for better compartmentalization of individual windows in the program. These are subprocesses (child processes) of the "Google Chrome" process that run in parallel, so though you should be able to force-quit individual renderers without bringing down the whole program, if you quit the parent process you will quit all active renderers as well.
This setup should allow you to more easily tackle hangs or other slowdowns caused by the renderer, by locating the ones using more system resources and quitting them in Activity Monitor if they cannot be closed by other means. However, if you do force-quit a Chrome renderer, you will be presented with an error in the browser that shows a little Google humor
Keep in mind the renderer for a window will only be active if you have rendered contents in the window, so if you create multiple tabs and do not load anything in those tabs, you will not have an active renderer for that tab or window.