SIP
A systematic investment plan puts a fixed amount into a fund every month. You buy more units when prices are low and fewer when they are high, and you do not need to time the market.
Lumpsum
Investing the whole amount at once. Over long periods, money invested earlier has more time to grow, so a lumpsum can end higher, but it also feels every fall at full size.
A simple rule
Salary every month: SIP. A bonus or maturity amount: split it over 6 to 12 months, or invest at once if you can sit through a fall without selling.
Step-up
Raising your SIP by 10% a year, as income grows, often adds more to the final amount than chasing a higher return.