What is TDS?
The payer deducts tax and deposits it with the government before the money reaches you. That payer can be your employer, your bank, your tenant, or your client. You do not wait until the end of the year to pay the whole tax. The government collects it through the year.
Tax is cut before the income is paid to you.
Deduction is monthly, or at the time of the payment, rather than one lump sum.
If TDS is more than your tax, claim the difference when you file the ITR.
TDS IS ADVANCE TAX
TDS is advance collection of your income tax, not a separate tax. Your final tax is worked out when you file the ITR. If TDS is higher, you get a refund. If TDS is lower, you pay the difference.