If you are wondering what is the secret CS statistic that appears on the character and weapon cards, read this page of the Tower of Fantasy guide.
CS stands for Combat Score. It is nothing more than a kind of value that indicates how powerful something is. This means that the CS on the character sheet is an indicator of your hero's strength.
The weapon also has this value. Remember, however, that CS is not the ultimate determinant of a weapon's power, as it can always be improved.