The CPU load is dependent upon the amount of time a server spends executing a script every time a visitor opens a page on a certain script-driven site. Static HTML sites use hardly any CPU time, but it is not the case with the much more sophisticated and functional scripts, that use a database and display dynamic content. The more clients open such a website, the more load shall be produced on the web server and if the database is very large, the MySQL server will be loaded too. An illustration of what may cause high load is a web-based store with a large number of products. If it is popular, plenty of people shall be exploring it all at once and if they search for items, the entire database containing all of the products will also be frequently accessed by the script, resulting in high load. In this light, having CPU and MySQL load data will give you an idea of how the site is doing, if it has to be optimized or if you just need a more efficient hosting solution - if the site is popular and the current setup can't cope with the load.