To create a page Drupal needs to make several database queries. This can slow down websites with a lot of traffic. To make websites faster Drupal stores web pages in a cache.

Clearing caches are relatively harmless. Sites might slow down for a bit afterward while the cache fills back up.

So if you have updated something on node pages but it won't be displayed to an anonymous user until cache cleared, but for single changes, it's not a good idea to clear full drupal cache.