There is a difference between 1st edition and 2nd Star Trek CCG cards. The major difference is the look of the cards. Also 1st edition is not compatible with 2nd edition. Though some 2nd edition cards are compatible with 1st edition. The different look of the cards are listed below.

These are 1st (1E) edition cards.                     

These are 2nd (2E) edition cards.                      

To know if a 2nd edition is compatible with 1st edition just check the lower left hand corner of the 2nd editions and you will find a 1st edition conpatibility icon (as shown on the Jadzia Dax Science Officer 2nd edition card above). The key to buying the right card is knowing the right card. Know your cards and your purchases will be satisfying. Happy buying and hope to do business with you soon.