The Procellarum KREEP Terrane, or PKT, is a large province on the near side of the Moon that has high abundances of KREEP.  KREEP is an acronym built from the letters K (the atomic symbol for potassium), REE (rare-earth elements) and P (for phosphorus), and is a geochemical component of some lunar impact breccia and basaltic rocks.  Notably, it is high in the KREEP element thorium, at a level of 4.8 ppm.  This is a major factor distinguishing it from the other terranes.  The PKT is on the near side of the moon, and covers 10% of the lunar surface, or 16% if one includes the maria lying within the FHT.  Despite this, it contains 60% of all basaltic flows.  KREEP has been shown to lower the melting point of rocks similar to those found on the Moon, and is expected to have contributed to volcanism in the region.
The Oceanus Procellarum and Mare Imbrium regions lie within the PKT.  In general, many maria, such as (but not limited to) Mare Frigoris and Mare Cognitum are members of the PKT.  Not all maria are in the PKT, however - Mare Crisium and Mare Orientale are located within the outer Feldspathic Highlands.
The PKT is the only terrane to lie exclusively in the near side of the Moon.  Human and robotic missions have been done to this terrane, and samples have been returned to Earth for further study.