HD3 currently has 496 different core cards, but in-game (for certain game modes and settings) players can encounter countless variations on these cards.
Cards can be gotten from winning duels, through the trader, or by completing achievements.
Custom cards, as encountered in game modes that support custom cards, can not be collected.
The core cards are the hardcoded cards which players can build decks from. By default, opponents will also have decks using exclusively core cards.
Custom cards can appear in certain game modes and are randomly generated. These cards will use the images found on cards from the Core set, and will often have a similar role as the original card, but beyond that there's no link with the Core cards.
Every non-legendary ship card in the Core set also has a mercenary variant. This card is similar, but generally more powerful than the original, and will have a different name while still using the same card image. When Mercenary cards are aquired, they receive a random upgrade, which modify stats or abilities on the card. The card pages for ship cards will list the Mercenary variation without any upgrades.
Every card in the Core set has a page on the wiki. Use the lists below to browse these pages.