“Clear Cache” is a popular phrase yet many haven’t cared to find out the meaning of cache. Cache can exist in several forms. In your browser, it could just be temporal files saved from web pages to save you some data and time when next your browser visits that specific web page again. Several images we see on certain websites are loaded from cache, rather than re-downloading the images again.
In the case of your blog, there are scripts that run on the server, interacting with databases and processing some functions to produce a web page. This can happen each time a visitor comes to your website. When the amount of running processes become excessive or gets over a certain limit, a website can crash or show a 500 Internal Server Error. A cache can be a saved version of a processed webpage on the server that is served to the browser when it requests for the content. This means that the webpage is generated once and saved, saving the server some computing resources.
But the issue with cache is that if you don’t set an expiry, it can keep showing old content even when you have updated the content of the page. If you use WordPress, there are many caching plugins that will help. Blogger.com won’t have this issue because Google already has a robust server on which the scripts run on.