C-Rank is one of the six classifications. It is preceded by D-Rank and followed by B-Rank. It is typically used classifying techniques intended for ninja of the chunin level. C-Rank techniques are often one of the first techniques a ninja will learn that require some amount of training.
There are also C-Rank missions. These missions are usually assigned to chunin, or in some cases, genin. Assignments include bodyguard duty and hunting wild animals, all of which will likely pose some risk to the ninja. The only known example of a C-Rank mission was Team Kakashi's assignment to escort Tazuna to the Land of Waves. After it was discovered that Tazuna had assassins after him the mission was stated by Kakashi Hatake to be B-Rank or even A-Rank. C-Rank missions pays between 30,000 and 100,000 ryo.