The short answer
Daghi rice has small natural marks on some grains, picked up in the field. It is the same variety (often 1121) and tastes the same once cooked, so it is sold at a lower price. It is a smart choice for daily chawal, fried rice and family meals.
Does it affect taste?
No. The marks are cosmetic. Length, aroma and cooking are the same as the unmarked grain. Where it matters is presentation: for a wedding table you might prefer a flawless grain, for a weeknight it makes no difference.
How to use it
Cook it exactly like 1121 basmati. Rinse, soak 30 minutes and cook by absorption or the boil-and-drain method.