There are many different types of holocrons in SWG.
These collection pieces are very rare and can be worth a lot. The most common holocrons are the 3/5 pieces and are the least valuable of all. The rarest is the Strange Sith Holocron 4/5 (Waist Pack).
These holocrons grant you the Meditate ability and the Belt of Master Bodo Baas, a wearable item. You can complete these collections to activate another collection, the Master Jedi Cloaks, for the Cloak of Hate and the Shatterpoint Cloak.
Pre-NGE Holocrons were hints at the class unlocks you needed to complete in order to unlock your Jedi slot. Players accessing holocrons would be told - quite directly - a class. In order to 'complete' that holocron, you needed to master that class. Once done, accessing another holocron would inform you of another class. These holocrons are nowadays used for nothing more than decoration.
This used to provide access to the online knowledge base system to contact cutomer support amongst other things. Now it has changed to the Help system which is an online non in-game system.
Star Wars LoreEdit
- Holocron on Wookieepedia