A mutual fund collects money from many investors and invests it according to a stated objective, managed by a fund house regulated by SEBI. Equity funds buy shares, debt funds buy bonds, hybrid funds mix both, and index funds copy an index. You own units, and their value is the NAV, calculated once a day after the market closes. You can invest a lump sum or through a monthly SIP, and you can redeem on any working day, with money reaching your bank in a couple of days for equity funds. Fees are charged as an expense ratio, deducted daily from the fund's value; direct plans have lower ratios than regular plans sold through distributors. Suppose you put ₹10,000 into a large-cap fund at a NAV of ₹50; you hold 200 units, which rise and fall with the fund's holdings. Funds diversify but do not eliminate market risk.