ctime originally meant creation time, however it has since been used almost always to refer to change time. It is updated any time file content changes (together with mtime), and also by changes in metadata such as file permissions, file ownership, and creation and deletion of hard links. In some implementations, ctime is affected by renaming a file (both original Unix and modern Linux tend to do this).
Unlike atime and mtime, ctime cannot be set with utime (as used e.g. by touch).
Read more about this topic: Stat (system Call)