Bypassing per site cache:
Enter the above code in the browser address bar and hit Enter key. This will fetch all the contents from the server instead of picking the elements cached in your browser(thus bypassing the browser cache).
Bypass Cache data for all websites(Global cache)
Settings > Privacy > CLEAR BROWSING DATA
Select the "Cache" Checkbox (and other options like Browser data, Cookies, Password etc if you want) and select "Clear".
For more interesting discusssion on the what does
F5 or force refresh does,
Read this SO post, What requests do browsers' “F5” and “Ctrl + F5” refreshes generate?