A turn (or round) is a brief period of time during a battle, which the actions of Fighting Friends are measured in. A character is able to perform (usually) only one action during each round before it expires, either by attacking, casting a spell, etc. After the current round passes, it is the enemy's turn, and one of their characters may act. This repeats until one side is defeated, or there are no characters are alive on the field, resulting in a draw.
Some powerful spells and attacks can take effect during the opponent's turn, such as Implosion or Melf's Acid Arrow. These do not count as anyone's turn, thus a side can appear to 'go twice.' Some conditions can also result in a wasted turn, due to the character coughing, dying, etc.