On this page of our guide to playing Ratchet & Clank, you will find out how the holocards work and what bonuses they add.
Holocards are one of the elements greatly influencing the gameplay. Normal cards are completely different than the unique RYNO ones (described in the "Collectibles" chapter), because they won't give you access to a unique weapon (apart from upgraded versions of the regular ones available in Challenge Mode). Instead, they offer powerful bonuses - increasing the amount of bolts you collect from enemies, a chance the enemy drops a Raritarium crystal, or a holocard.
To get the bonus, you must complete one of several dozens of card sets. Those are made from 3 cards linked in some way with each other. When you collect all 3 cards of a set, it will be activated and you will be given the bonus that comes with it. Fortunately, the cards are collected randomly and you don't have to look around every corner. They will be dropped from enemies - some can also be acquired during the exploration of planets.
You should remember that each card that you already have will be treated as a duplicate. The amount of duplicates can be found by going to the menu, and then selecting the "Card Collection" option. Each 5 duplicates you have can be used to trade for a new card you haven't collected. If you lack a single card to activate a set, and you have at least 5 duplicates, highlight the card you want to acquire and press the button shown on the screen to perform the "trade".