Well as the name implies, the history on your browser, is a list or collection of web pages you've visited since the last history clearing was performed.
In most web browsers, pressing CTRL+Shift+Del will allow you to erase your browser's history. You should also clear the browser's cache.
When you visit a website, that site is stored locally in a cache in case you visit the page in the future. This is faster than having to redownload the page from the web server. In theory, its good but a lot of websites are dynamic. That means that the content is constantly changing. It wouldn't make much sense to store a copy of Facebook since it is always changing.
Some websites may act odd when the cache is outdated, such as not working properly or at all.
I usually recommend people to erase their history and cache when websites aren't loading properly or working at all. Most of the time, that solves a lot of issues. In most web browsers, clearing the cache is also in the same menu as clearing the browsing history.