Hi,
As rightly described by Swastik, mediclaim refers to an insurance policy under which all the employees are covered. The premium for this policy is paid by the company on behalf of the employees, and there are companies which show premium paid to the third party as a part of CTC.
In mediclaim, dependents of the employee are also covered as per the conditions of such policy. Cashless facility is available, and some companies provide PHS cards (Insurance cards) for the employees and their dependents.
Medical allowance is a benefit given by the company and is a part of CTC. Amounts up to 15,000 are non-taxable if you produce the bills; any amount over and above 15,000 is taxable.
This benefit is provided because most mediclaim policies do not cover sickness or injuries where the employee did not stay for 24 hours in the hospital.
I hope the difference is clear to you.
Cheers,
Archna