It is important to understand that a page can be cached (held for future viewing) in multiple ways. If you have edited and published changes to a page but still see the old version of the page when refreshed, there are a few possible culprits.
Clearing Browser Cache
When using a web browser it often caches webpage data locally on the device to reduce load times on subsequent visits to a page. This can be troublesome when you have edited a page and want to see the end results. The easiest method to ensure an entirely fresh version of a page, and to see the changes you've made, is to clear your browser cache and refresh the page. Indiana University has an excellent page describing how to clear the cache on a wide range of web browsers.
In most modern browsers you can disable the local cache entirely. This is typically not necessary, but if you are experiencing significant local caching issues this may be a good option. A simple Google search should lead you to instructions on disabling the cache for your specific browser.
Varnish Cache is a technology we are using to ensure that pages load quickly under heavy web traffic loads. As long as you are logged in to a session and see the CMS toolbars at the top of your page you should not need to worry about Varnish Cache. You should however understand that any changes you make can take up to 5 minutes for users who are not logged in to the CMS to see. When a page is visited by a regular user it is cached for the next 5 minutes. Anyone who visits that page over the next five minutes will see the cached version of the page. You can see if your changes are viewable to the public by logging out and hitting the page to see if they are live yet. You can also switch your URL from https to http to see the Varnish Cached version as your CMS session is only active on https.