Academy
The lowest level of the ninja ranking system in the Naruto world. The students learn through broad theoretical ninja abilities, also known as jutsus and perform basic jutsus such as the replacement technique whereby the user has the ability to replicate himself or other people that he desires to replicate. Students graduate from the academy by passing the final exam.
Genin
Achieved after graduating from the ninja academy by wearing a headband which symbolizes their respective village. The ninja's life begins here as they are exposed to different levels of mission and apply their jutsus during battles. Ninjas are expect to perform D rank jutsus like simple replication technique.
Chuunin
After a few missions, the students would enter into the chuunin exams divided into 3 stages; multiple choice test, forest of death and sudden death tournament to complete the whole exam.
The exams are slightly different to genin as the ninjas have to work together in order to accomplish their common goal.
For instance, in Forest of Death, both Sasuke and Naruto combined their efforts to overcome a group of ninja from the rain village to gather one of the scrolls required in the mission.
The exam also test the ninja's ability to make the right decisions and working as a team.
Jounin
The jounins normally perform B rank jutsus and have the responsibility to protect the village as a whole. They also have to seek new missions and lead their own team like for example, Kakashi of Team 7, Naruto, Sasuke and Sakura. Some jounins tend to participate in specialized jounins or ANBU which is a group that conduct top secret missions and must conceal their true identity from the other ninjas.
Kage
The highest ranking ninja in the Naruto world. Ultimately posses all the rank jutsus from A to S but more commonly posses the A rank and S rank jutsus also known as kinjutsus or "forbidden" jutsus which cause harm to the user. The most notable example is the sealing jutsu performed by the fourth hokage in sealing the kyuubi into Naruto's body. Other examples are Naruto's ability to perform kage bunshins and the cursed seal technique performed by Sasuke.
Also known as one of the most powerful ninja in one of the 5 powerful countries; Konohagakure (Hokage), Sunagakure (Kazekage), Kirigakure (Mizukage), Kumogakure (Raikage) and Iwagakure (Tsuchikage).
The leader of the ninja society, treated as being equal with the rulers of their country, oversees the activities of their villages, sometimes consult with the higher ups people, sending and allocate teams into missions and making decisions regarding the safety of the village.