Under Income Tax Act following types of allowance are defined

House Rent Allowance:
Under sections 10(13A) of Income Tax Act, 1961 allowance is defined as an amount received by an employee paid by his/ her employer as a rent of his/her house. It is a taxable income. There is no exemption in tax if he is living in his own house or house for which he is not paying rent. There are following amount which are exempt from tax:
Actual house rent paid by that individual
Rent paid for the accommodation over 10% of the salary
50% of the salary if house is placed at Delhi, Mumbai, Kolkata, Chennai or 40% of the salary in it is placed in any other city
Entertainment Allowance:
It is the amount paid by employer for availing entertainment services. Under section 16(ii) of Income Tax Act, 1961 it is entitled to deduction in tax from is salary. But in this case deduction is given to his gross salary which also includes entertainment allowance. Deduction in tax against this allowance can be divided into two parts :
In case of Government employee entitled to minimum deduction of
Entertainment allowance received
20% of basic salary excluding any other allowance
Rs. 5000 In case of other employee entitled to minimum deduction of
(a) Entertainment allowance received
20% of basic salary excluding any other allowance
Rs. 7500
Entertainment allowance received during 1954-1955
Other Special Allowances
Children Education Allowance
Tribal Area Allowance
Hostel Expenditure Allowance
Remote Area Allowance
Compensatory Field Area Allowance
Counter Insurgency Allowance
Border Area Allowance
Hilly Area Allowance

Allowances for there is a provision of exempt in income tax are:
Allowance given to a citizen of India, who is a government employee, for rendering services outside India
Allowances given to Judges of High Courts
Allowance given Judges of Supreme Court
Allowances received by an employee of UNO

What is Perquisite
Under section 17(2) of Income Tax Act, 1961 perquisite is defined as:
Amount paid for the rent-free accommodation provided to the assessee by his employer
Any concession in the matter of rent respecting any accommodation provided to the assessee by his employer
Any benefit or amenity granted or provided free of cost or at concessional rate in any of the following cases:
1. By a company to an employee, who is a director thereof
2. By a company to an employee being a person who has a substantial interest in the company
3. By any employer to an employee whose income under the head 'Salaries' exceeds Rs.24000 excluding the value of non monetary benefits or amenities
4. Any sum paid by the employer in respect of any obligation which, but for such payment, would have been payable by the assessee
5. Any sum payable by the employer whether directly or through a fund, other than a recognised provident fund or EPF, to effect an assurance on the life of the assessee or to effect a contract for an annuity

There are following perquisites which are tax free:
Medical facility
Medical reimbursement
Refreshments
Subsidised Luch/ Dinner provided by employer
Facilities For Recreation
Telephone Bills
Products at concessional rate to employee sold by his/ her employer
Insurance premium paid by employer
Loans to employees by given by employer
Transportation
Training
House without rent
Residence Facility to member of Parliament, judges of High Court/ Supreme Court
Conveyance to member of Parliament, judges of High Court/ Supreme Court
Contribution of employers to employee's pension, annuity schemes and group insurance

Deductions from Salary income
Certain deductions are available while determining the taxable salary income.

A) Standard Deduction
Income tax slabs 2009-2010 (for Men) in India:
Income Tax Slab (in Rs.) Tax
0 to 1,60,000 No Tax
1,60,001 to 3,00,000 10%
3,00,001 to 5,00,000 20%
Above 5,00,000 30%

Income tax slabs 2009-2010 (for Women) in India:
Income Tax Slab (in Rs.) Tax
0 to 1,90,000 No Tax
1,90,001 to 3,00,000 10%
3,00,001 to 5,00,000 20%
Above 5,00,000 30%

Income tax slabs 2009-2010 (for Senior Citizens) in India:
Income Tax Slab (in Rs.) Tax
0 to 2,40,000 No Tax
2,40,001 to 3,00,000 10%
3,00,001 to 5,00,000 20%
Above 5,00,000 30%

B) Professional Tax
Professional tax, which is paid, is allowed as deduction.

C) Arrears salary
If salary is received in arrears or in advance, it can be spread over the years to which it relates and be taxed accordingly as per section 89(1) of the Income tax Act.