Hand Seal

Hand seals, called hand signs in the English dubbed version, are used to create many ninjutsu, genjutsu, and other secret arts other than taijutsu. There are different sequences of hand signs for every technique, requiring memorization. While techniques may require a number of hand signs to work, a skilled ninja can use less or even one to perform the same technique. An example of this is the Water Release: Water Dragon Blast Technique, which requires a total of 44 hand signs to activate. The Second Hokage however just needed to use one hand sign to complete the technique, a testament to his skill.

Besides the 12 traditional hand seals, each named after an animal of the Chinese zodiac, there are unique hand seals used for certain techniques. These hand seals are rarely seen, and can be considered unique to specific jutsu. An example of such is Haku's Demonic Ice Crystal Mirrors.

Hand Sign Examples
And I will have you know hand signs, jutsu, chakra, etc. are all perfectly real if done properly and you believe. Not lying.

Trivia

 * Rat is often used in the Nara Clan's Shadow Jutsus
 * Tiger is often used in Fire Release and Water Release jutsus
 * Snake is often used in Earth Release jutsus and in Wood Release
 * Dog is often used in Ice Release by Yukigakure ninja
 * Hare also means Rabbit
 * Serpent also means Snake
 * Ram also means Sheep
 * Bird also means Rooster
 * Boar also means Pig
 * Rat means Nezumi/Ne in Japanese
 * Ox means Ushi in Japanese
 * Tiger means Tora in Japanese
 * Rabbit/Hare means U/Usagi in Japanese
 * Dragon means Tatsu in Japanese, or Ryuu when used in Jutsus
 * Serpent/Snake means Mi/Hebi in Japanese
 * Horse means Uma in Japanese
 * Sheep/Ram means Hitsuji in Japanese
 * Monkey means Saru in Japanese like Sarutobi the Third Hokage
 * Rooster/Bird means Tori in Japanese or possibly Dori? in Chidori
 * Dog means Inu in Japanese
 * Pig/Boar means Buta/I in Japanese