There may be many reasons why a kitten bites a cat. This could be because they are playing or practicing their hunting skills, or it could be because they feel threatened or uncomfortable. Cats are likely to be "targets" when kittens are playing or practicing their hunting skills. If kittens bite during play, this behavior can usually be reduced by giving them more suitable toys to help them release their energy.
If your kitten is biting because they feel threatened or uncomfortable, you may want to observe their environment to see if there is anything that might be causing the factors in this reaction and consider how to correct the situation. Overall, if your kitten engages in inappropriate cat biting behavior, it is recommended that you consult a professional veterinarian or behavioral counselor to learn how to properly handle the situation.