Think of Burn as Poison with a Coin Flip. Between every players turn, if your Active is burned, you flip a coin. If Heads, nothing happens. If Tails, your burned Active takes 20 damage.
Yoshi is correct, the wording is "Place" which is a subtle but important difference. I've noticed an increasing number of attacks and effects are using the word "Place". It's a conspiracy!!! :lol:
Now remember, it is a Special Condition, so it can be removed by benching or anything else that gets rid of all Special Conditions. Char, however, is perminant.