To help loading pages, browsers cache most of the content that appears on the webpage, saving a copy of the webpage's content on the devices hard drive. This way, the next time the user loads the page, most of the content is already stored locally and the page will load much more quickly.
If you are experiencing an error are not seeing changes that you expect on a portal page or course you will need to clear your cache. Once a browser cache is cleared, every webpage that loads will load as if it is the first time the user has visited the page. If something loaded incorrectly the first time and was cached, clearing the cache can allow it to load correctly.
Search for "cache" in your browser settings and clear "Cached images and files" browsing data. Don't clear cookies data to stay logged in.