TDS is mode of deducting tax by someone who makes a payment to another, such as Employer deducting tax at source from salary of employee u/s 192, Bank deducts tax on interest on fixed deposits u/s 194A whereas TCS is a form of collecting tax, for example the seller collects tax from the buyer at the time of sale of specific category of goods or utilization of services/facilities like, tax collected at toll plaza, parking lot etc.