Chrome, like most other browsers, caches content from websites you visit in order to improve performance.
Sometimes, though, things can go wrong and cause you to want to dump the cached data. This is especially common when developing website pages or web applications, but may also be necessary in other situations where you want to be sure you’re displaying up-to-date data from the server.
If Chrome’s web tools are open (and if not, you can open them using F12) the Reload button on the Chrome toolbar gains some new abilities. Right-clicking on the button now opens a menu offering three reload options:
The three options offered are:
Normal Reload, using any previously-cached data (same as F5)
Hard Reload, causing the browser to re-download resources, but allowing subsequent calls to resort to the cached version, which is not cleared by using this option
Empty Cache & Hard Reload, causing the page cache to be emptied and everything re-downloaded.
Note: I can verify this for Windows and Linux machines, but haven’t tried it on Mac.