What is volatility? Is it like playmaking ability? Is the higher the number better? Is it a good or bad trait?

Volatility is how susceptible a player is to booming or busting. The higher the volatility the more a player will either go up or down compared to their potential rating. The lower the volatility the more likely they will hover around the potential rating they start with. If you like to take chances the higher the better, if you want a player to be who you think he is try to get lower. It makes the draft much more interesting :)

not taking anything away from Bryson's explanation, nor punisher's excellent practice of showing the actual link, here is the original explanation from JDB:

https://mfn73.myfootballnow.com/community/thread/1/2045?page=1#13052

A new attribute 'Volatility' has been added to the player attribute list. This attribute has always been assigned to players, but has never been exposed to you as the owner. What this attribute indicates is the likelihood that the 'future' value is going to change - a player with 0 volatility will probably not have much movement in his future value, so it would be safe to say that he will max out wherever his future value is set to. A player with 100 volatility, however, will very likely -not- resolve to his future value. You don't know, though, whether a 100-volatility player will have his future value boom or bust. This will make drafts more interesting, because you might be less inclined to take that 99-rated QB with 100 volatility in the first round, knowing he is at least 50% likely to bust; on the other hand, that 50-rated WR with 100 volatility in the 7th round is much more worth taking a chance on.

It's the bane of drafting now. /sarcasm font/