Chickens are birds which are kept on a farm for their eggs and for their meat.

If someone calls you a chicken, they mean that you are afraid to do something.

If you say that someone is counting their chickens, you mean that they are assuming that they will be successful or get something, when this is not certain.

If you describe a situation as a chicken and egg situation, you mean that it is impossible to decide which of two things caused the other one.

If someone is running round like a headless chicken or rushing around like a headless chicken, they are panicking when they should be thinking carefully about what needs to be done.