DII stands for Domestic Institutional Investor. These are large Indian institutions such as mutual funds, LIC and other insurers, banks and pension funds like the NPS. They invest money pooled from millions of Indian households, and their monthly SIP inflows into mutual funds have become a major, steady source of buying in the market. Exchanges publish daily figures of DII net buying or selling, often compared with FII flows. On many days when foreign investors sell heavily, DIIs are net buyers, which cushions the fall. A headline like DIIs bought ₹3,000 crore while FIIs sold ₹4,000 crore describes that tug of war. For a retail trader, these flows are context, not a trading signal; institutions have different horizons and constraints. But watching the data over months shows who has been supporting or pressuring the market.