Rupee cost averaging is a natural side-effect of investing a fixed amount regularly, such as through a monthly SIP, rather than investing a lumpsum all at once. When the mutual fund's NAV, or price per unit, is low, your fixed monthly amount buys you more units. When the NAV is high, the same fixed amount buys you fewer units. Over time, this evens out your average purchase cost per unit.
The practical benefit is that you don't need to correctly predict whether the market is about to rise or fall — you automatically buy more when things are cheap and less when things are expensive, without having to time anything yourself. This doesn't guarantee profits or protect against a market that falls continuously for a long stretch, but over a typical multi-year investment horizon with normal market ups and downs, it tends to smooth out your entry price meaningfully.