The game offers a turn-based battle system. However, new strategies can be played with the inclusion of Brave and Default commands in the game. Players and enemies will start the battle with a certain number of BP or Brave Points. These stand for the actual actions a character can perform and will usually start with a default value of 0. If a character starts the turn with a negative BP, he/she won't be able to act at all.
Selecting Brave will consume 1 BP and will allow you to act up to four consecutive times. BP can reach negative values so it is possible to take consecutive actions even when you start with 0 BP. The risk however, is that the character with negative BP won't be able to act until the BP is back to 0.
Going on Default however, puts the character into a defensive stance which will minimize the damage he/she will receive and start the next turn with an additional BP. A character will normally have a maximum of 3 BPs (4 BP if you have the Templar support ability) so once you've reached that number of stacked BPs, you can go all-out and use Brave up to four times without going on a negative value.
There are abilities that specifically consume BP to be activated. A few good examples will be the Valkyrie's attacks. Even if a Valkyrie attacks with full stacked BP, he/she can still reach negative BP value if the user opted to act consecutively and use BP-extensive moves.
There are also certain abilities that will allow you to manipulate BP at will. This will either allow you to increase the BP of your allies, allowing them to act earlier without Defaulting too much or allow a character with negative BP to act again on the next turn. Some good examples of these are the Merchant's BP Drink skill, the Performer's One More for You and My Hero, the Spiritmaster's Convert BP and the vampire's Battle Thirst to name a few.
You can also prevent your enemies from getting extra actions by removing their stacked BPs as well. Some of these examples include the Swordmaster's Squeaky Wheel, Performer's Zero Sum or the Spiritmaster's Moderation.