Tight oil is a unconventional oil that is found in reservoirs with very low permeability.
I suspect that “tight” is still less expensive to extract than shale. It surprises me. I grew up in Carlsbad and played in the deserts around there. I haven’t be back in a long time but I love to check Google Earth for places I loved as a boy. I thought there were a number of oil wells in the area growing up but what is there now is ridiculous.