Caching increases the apparent speed of the website by storing copies of the pages on the server on the browser and keeping the copies in memory. It appears much faster because it takes far less time to grab page from memory than it does to parse the page every time it's accessed.
This can speed up the user experience, so enabling cache is usually good. It is a bit frustrating while you're building the site, because you don't always see your changes immediately.
This tells you how to access the cache settings, to enable, disable or clear your Drupal 7 cache.
Step 1. Access the cache settings
In order to increase the performance of Drupal, especially for busy sites, you may want to enable caching. To enable caching, follow the directions below:
Log into Drupal as Administrator and go to Site Configuration > Performance.
Step 2. Activate cache
Select the checkboxes under Caching and click Save Configuration. That's it. Caching is now setup.
You can refine the caching by using the additional settings, and choosing time limits from the two dropdown boxes, but in most cases this is all you need to do.
Note: Clear Cache - this will clear current cache. If you are having trouble with viewing changes you make, they may be due to cached copies of generated pages stored on the server. This button will clear them. With Drupal, you may have to do it more than once. If you need to be cleaning the cache reguarly, consider using the Administration Menu module which provides a quick and easy link to the Clear Cache button.