FII (Foreign Institutional Investors) refers to institutional investors from outside India who invest in the Indian financial market.
DII (Domestic Institutional Investors) refers to institutional investors based in India who invest in the domestic financial market.
FIIs and DIIs usually form about 35% of the activity of India's stock exchange activity and heavily influence the stock markets. When an FII or a DII invests in a company, it usually gives confidence to a large number of retail and individual investors.
When FIIs/DIIs are investing in some particular company, it is a good hint for us that the stock might perform in the future and we can invest in such a company.
So money inflow in the FII/DII Data work as a good indicator. We can do the same when they are taking an exit from a stock.