When trying to tweak CSS style of websites built with RT template, I often come across CSS files with parameter, like "<link rel="stylesheet" href="/zhzht/plugins/editors/rokpad/assets/styles/rokpad.css?cache=2.1.6" type="text/css">"
Now from itself I can tell the parameter has something to do with cache, but is there any place where I can find full explanation about this mechanic? How does the parameter works? How to conduct it properly? When to use it... etc. I goolged it but found no answer.