Q: What is the Difference Between a Progression Server and a "Classic" server?
By most descriptions, a "Classic" server is an attempt to recreate EverQuest exactly as it was at launch, using only assets and content that was available in March of 1999.
A Progression Server is another EverQuest server, and therefore runs alongside existing servers. It contains many changes that have been made to the game since 1999, such as maps, Krono, a more configurable UI, the removal of "Hell Levels" and race/class experience penalties, custom chat channels and serverwide or cross-server communication, the ability to memorize spells via right-clicks, the ability to "Find" specific NPCs or locations, and many other enhancements.
In cases where we have updated or changed the layout of zones, Progression Servers use the updated version of the zone geometry. In cases where we have changed items or player abilities, Progression Servers use those updated abilities. In cases where items were completely removed, those items will either stay removed or be available for a very limited time on Progression Servers. In cases where zone population was changed, you may not find all of the NPCs you remember in exactly the same places they were before, or you may encounter new NPCs with new loot that wasn't there before.