Vacation is a mode that "freezes" your account which means that when you activate it you don't gain Resources, cannot be Attacked and cannot play at all. When you activate Vacation mode all training, Building and Upgrading processes stop and continue automatically after the Vacation has expired. No Marches can be sent from and to the Castles of the player who is in Vacation, but all already sent Marches will reach their targets and will be processed on time (i.e. Vacation mode protects players from the future attacks to their accounts and not from the ones that has already been sent).
Note that you cannot go into Vacation mode if you have an active Support or Camp March.
Activation of the Vacation mode is free and its duration is 20 days. You can stop the Vacation mode before the 20-days period has expired for free but note that if you want to stop it in the 48 hours after activating it, you must pay 200 Coins.
Note that you can activate Vacation mode for the second time 48 hours after the first Vacation has expired.
During a Vacation mode a player's Castles don't give any points for the Clan ranking.