A mutual fund is simply a pool of money managed by a professional who invests it in other company stocks (share in profit) or bonds (given out as loans). The pool then generates income which is either added to the pool (growth) or passed back to investors (dividend).
When you invest, ensure you only do in Direct Plan Mutual Funds. You then get upto 40% more in long term portfolio size by avoiding commissions and brokers. Use an app like Jama to get started with mutual funds.