Hi Amar,
Cost to Company can be used to refer to the total cost that an organization is spending towards their employee including the Salary, Perks, Cost related to benefits, Cost related to hiring, Training, Retirals, Statutory Contributions etc. In general, the CTC can be defined as:
CTC = Direct benefits + Indirect benefits + Saving Contributions
You can also use the Research tab given here as that would help you, go through different threads discussed on the same topic, earlier.
In humorous terms - Cost to company is a trick of a company and HR department, to show that they are paying a big salary, but unfortunatly it is just bubble :)