A depository is an institution/organization which holds securities with it in Demat form. And Depository Participant ('DP') is the agent or the registered stockbroker of such depositories. CDSL (Central Depository Securities Limited) and NSDL (National Securities Depository Limited) are depositories registered by the Indian government to hold multiple forms of securities like stocks, bonds, ETFs, and more in Demat form.
Demat transaction charges are the DP transaction charges levied by CDSL on all Sell transactions from your Demat holdings (Equity Delivery). Irrespective of the value of the shares sold. They are Rs. 18.50 + GST per share per day.