Jutsu, or skills/techniques, are the mystical arts a ninja will utilize in battle. To perform a jutsu, the ninja will manipulate their chakra and may use some form of hand seal. Some techniques like Taijutsu do not require hand seals, however the ninja may use them to focus their chakra to certain areas of their body. Also some Ninjutsu like Rasengan and various weapon utilizations do not require any hand seal use.
By forming hand seals, the ninja is able to mold their chakra and manifest the desired jutsu. Because of the extensive number of hand seals and different combinations, there are thousands of potential jutsu to be discovered and used. The hand seals themselves come from the twelve signs of the Chinese Zodiac. The appearance of the seals stem from Hindu and Buddhist iconography, and are called "Mudra" meaning "seal" or "sign" in Sanskrit. These hand gestures helped identify the nature and function of the deity who used them. Over time the positions and traditions changed as they were adopted and moved from country to country.
In addition to these hand seals, certain jutsu have their own unique hand and finger positions, such as the gestures used in Kage Bunshin, Shintenshin, etc.. Every ninja in the series save for one has used both hands to form seals. Haku used one-handed seals in his Hyouton bloodline limit techniques. It is unknown if this was a skill unique to the whole of the bloodline or merely Haku himself. Note this is different than the one handed chakra focusing gesture one sees a lot of ninja use.
Ne - Rat
Ne is the First sign of the Chinese zodiac, the Rat. It is associated with North and the month of November.
Note: Rat is used in the Nara clan's shadow manipulation.
Ushi - Ox/Cow
Ushi is the Second sign of the Chinese zodiac, the Ox. It is associated with North-Northeast and the month of December.
Tora - Tiger
Tora is the Third sign of the Chinese zodiac, the Tiger. It is associated with East-Northeast and the month of January.
Note: Tiger has been associated with Fire Element manipulation.
U - Rabbit/Hare
U is the Fourth sign of the Chinese zodiac, the Rabbit. It is associated with East and the month of February.
Tatsu - Dragon
Tatsu is the Fifth sign of the Chinese zodiac, the Dragon. It is associated with East-Southeast and the month of March.
Mi - Snake/Serpent
Mi is the Sixth sign of the Chinese zodiac, the Snake. It is associated with South-Southeast and the month of April.
Note: Snake has been associated with Earth Element manipulation.
Uma - Horse
Uma is the Seventh sign of the Chinese zodiac, the Horse. It is associated with South and the month of May.
Hitsuji - Ram
Hitsuji is the Eigth sign of the Chinese zodiac, the Sheep. It is associated with South-Southwest and the month of June.
Note: Ram has been officially depicted in the manga as having either the right thumb or index finger extended upwards.
Saru - Monkey
Saru is the Ninth sign of the Chinese zodiac, the Monkey. It is associated with West-Southwest and the month of July.
Tori - Bird
Tori is the Tenth sign of the Chinese zodiac, the Rooster. It is associated with West and the month of August.
Inu - Dog
Inu is the Eleventh sign of the Chinese zodiac, the Dog. It is associated with West-Northwest and the month of September.
I - Boar/Hog
I is the Twelfth sign of the Chinese zodiac, the Pig. It is associated with North-Northwest and the month of October.