What do some repacks mean to "Remember to Clean Ur Cache"?

[foxtrot08]

As some repacks say, "Remember to clean cache". What does this mean? And how do i do it?

[skull5005]

Well there's a folder in your World of Warcraft directory called "Cache" it saves certain NPCs and equip ids and stuff, deleting the cache folder will allow you to see new things in the repack.

Hope I helped