Genin is lowest rank of ninja, usually genins doesn't have many techniques or skill.
When academy student become a ninja, he will have two "ninja teammate",
one team contain three genin and one jounin wich is their "teacher".
Also when academy student become genin,
he will get forehead protector usually ninjas wear it on head just like name says,
but you can also wear it at your hand, stomach etc.
Chuunin is second rank of ninja. There is just one way to become chuunin: pass the chuunin exam. "Chuunin ninjas" are much rescpected than Genin, and usually chuuninshave more techniques than Genins. One of chuunins duty is to be teacher at academy student to teach teachniques like ( bunshin no jutsu,henge nojutsu etc. ) or chakra controling, and other simple things. Chuunins also obtain a uniform wich look like jounins uniform. Chuunins can handle difficulter missions and other difficult orders.
Jounin is very high-class ninja. Jounins are highest level of normal ninjas. Jounins are very strong and they have many techniques ( jutsus ).Usually jounins duty is to teach&train three-genin-team when this Jounin is their teacher. If jounin is teaching genins, usually he teach chakra controlling: walking on the water,tricks, techniques etc. In wars high-class ninjas just like jounins are very important. Jounins have forehead protector, uniform and some kinda scroll pouch where theyuse maps, or other usefull little stuff for bad situation. And sometimes Jounins have own powerful jutsus just like Kakashi, Kakashi also have 1000~ different techniques.
Every ninja countys have many genins, there are many chuunins, and many jounins,
but there is just only kage. Kage is the most strongest ninja in that village. Kage will be
choosed by elders in that village. Kages will risk their life in the war, or battle at wherever.
Kages wear robe and a cap where is written that contry "name" like fire,water and it color.
Each of the hidden villages have their own kage with different name. Fire (Ho),Wind (Kaze),
Lightning (Rai), Water (Mizu), Earth (Tsuchi).