Advance Tax is a tax that you are required to pay tax to the government on your income throughout the year as you earn this income.
If advance tax not paid on time, the taxpayer shall be liable to pay interest u/s 234b and Interest u/s 234C
For salaried individuals, advance tax payments are mostly taken care of by your employer in the form of TDS. However, if you have interest income from fixed deposit etc which is more than Rs. 10,000 you should calculate your tax due as you may have to pay advance tax.
Freelancers and business owners must pay advance tax. To know how to calculate your advance tax or interest under sec 234A / 234B / 234c and by when; by referring to this page.