Glossary

Chakra- the fusion of physical and mental energies

Kekkei Genkai- usually a fusion of two chakra attributes i.e. Lava Style = Fire + Earth. It also refers to special abilities passed down in certain families i.e. Sharingan from the Uchiha clan.

Ninja/shinobi Ranks:

Genin (Low Ninja)- Ninja School Graduate

Chunin (Journeyman Ninja)- Have achieved a certain level of maturity, they possess leadership skills and tactical prowess

Tokubetsu Jonin (Special Jonin)- They are elite chunin, who despite being skilled aren't yet at the level of Jonin. They usually possess a single skill in which they excel. 

Jonin (Elite Ninja)- a highly experienced and skilled ninja who typically serves as a military captain in their respective ninja villages

Kage- leaders of a ninja village i.e. the Hokage of Konoha

Techniques:

Genjutsu (Illusion Technique)- uses chakra to trap an opponent in an illusion by interfering with their chakra flow

Taijutsu (Body Technique)- the use of martial arts or the optimisation of natural human ability, does not use chakra

Ninjutsu (Ninja Technique)- uses chakra, usually in combination with hand signs, and refers to anything that isn't Genjutsu or Taijutsu

Fuinjutsu (Sealing Techniques)- a type of jutsu used to seal objects, living beings, chakra etc. within another object. The presence of a seal is indicated by the appearance of several black marks that are usually just Kanji

Ninjutsu Ranks:

E-Rank = The most basic techniques, used by academy students

D-Rank = Can be learned by Genin

C-Rank = Usually used by Chunin, but some Genin are capable of using them

B- Rank = Used by Jonin, has high chakra requirements

A- Rank = Used by Jonin/Kage

S- Rank = Esoteric techniques that are exceedingly difficult to learn, often unique to a single user

5 Great Shinobi Villages:

Konoha

Iwagakure

Kumogakure

Sunagakure

Kirigakure