These are alternate art versions of some specific cards, but given a special art treatment and printed at very low distributions hence has very high collector's value.
Parallel arts do not have any specific indicator on the card, and shares the same rarity symbol as its original (so a parallel art rare will still be indicated with an R). However, they are always fully-foiled. Parallel art cards exist for all rarities, even for common cards.
Features: they are always fully-foiled, but otherwise without any specific design language hence allowing the artist to be creative.
Approx. probability: 0.35% (non-SEC), 0.12 (SEC)
Approx. market price: approx. 2X higher than the non-parallel.