06 January 2014
the basic concept is simple. To ensure that the government receives tax revenue on a regular basis instead of at the year end, provisions were inserted in the income tax act directing tax payers to pay part of their tax liability on the estimate basis on or before per-determined dates. This ensured that the government receives regular tax revenue. In a way, it was helpful to tax-payers also as it evened out their tax liability across the year instead of bulking it at the year end.
Refer this link for how to compute advance tax, due dates for payment etc http://taxguru.in/income-tax/advance-tax-provisions-in-brief-download-advance-tax-payment-challan-and-utility-to-pay-income-tax-online.html