The Revelation Flow is the way one acquires new skills in Rogue Galaxy. To unlock these, you must find or buy items to put in slots. Note that the sets of skills are linked and sometimes require you to get the ability before it.
There are two different kinds of skills, ones that grant you innate stats (like increased HP or attack) and ones that grant you in-battle abilities. All items for the Revelation Flows will eventually become available in shops towards the end of the main story, and all shops will have unlimited inventory on a second playthrough.
