are you new to pokemon? you really don’t have to worry about fake cards that much any more . that was more of a serious thing back when pokemon first came out and everyone wanted to get there hands on as much pokemon merchandise as possible. as long as you dont buy them of the street or in a flea market , you really don’t have to worry about them being fake. but just in case you still want make sure there real just try out what beatiful-swablu says, because real cards aren’t really transparent trough light. but if that still doesn’t convince you could also try taking your index finger and your thumb, put one on top, the other on the bottom of the card then press them until both ends meet. if its real you wont notice bend marks across the middle , if it is fake , the card will be completely damaged. do it carefully though .