Caching allows for data to be stored and quickly retrieved when requests are made. However, sometimes when a cached item is updated you may not see the updates you've made even after you published them to the live site even though you can see the changes in preview. When that happens refreshing the cache (also known as busting the cache) purges the stored items and retrieves the latest items for storage. Once the cache is refreshed users will be able to see the updates that they've made.