We all know how this works but Im putting this for new members who are not so familiar with the System.
Academy Student: This is the E-Ranked Level of Shinobi and usually are around age 7-11 in this Rank. They advance to the next level that is given by a Chuunin Teacher of the Academy.
Genin:This is the D-Ranked Level of Shinobi and are usually stuck doing the grunt work of the Village such as picking weeds and finding herbs.They gain the next Rank in the Shinobi ladder by doing a series of tests and battles involving a test of Will or knowledge, A survival test that tests the knowledge of restraint of forbidden fruit and battling shinobi at the same time.The third test is a test of Shinobi knowledge and tactics in the face of an advesary.
Chuunin:Chuunin are the C-B ranked Shinobi. They are usually monitoring the chuunin exams or teaching the Academy students.Chuunin usually advance to the Next Rank of Jounin by a selection phase made by the Hokage. Once they reach the right abilities they are promoted by the kage of their village.
Special Jounin: They are usually B-A Ranked. They Excel In ONE style of fighting and were made Jounin because of it. Once they balance all their skills they are then Refered to As Jounin.Im Some cases they do not take on a Ninja team(Genin) Anko Mitarashi for example.
Jounin: Jounin are B-A Ranked Shinobi(Under certain cases such as Kakashi Hatake they are refered to as Joui-Jounin or S-Ranked Jounin)These are the Elite shinobi of the Village entrusted with A-S ranked Shinobi missions.Jounin are assigned a Genin team to train so they can become Chuunin and help the village.
ANBU(And Root): Anbu are the A-S Ranked Shinobi Assassins of the Villages.They wear Masks and robes to hide their identities, They are usually the Kage body guards when they are near another Shinobi village.
Sannin: The Sannin of a village are Decided by a very well known Shinobi such as Salamander Hanzou with Jiraiya,Tsunade,Orochimaru. They are revered through out the Shinobi lands as great Ninja.
Kage:The Leaders of the Ninja Villages, S-Ranked and experienced in many Shinobi arts.They give missions to the Shinobi of their Village and usually command armies in a war.