 XP can be used to increase a profile's level, which unlocks more profile customization options, increases the friend limit cap, and raises the probability of "booster pack" trading card drops.Steam Trading Cards are distributed through several methods; if a game has a trading card set, playing that game will periodically grant the player trading cards until a threshold is met.For most games, this threshold is reached once the user has received half the number of cards required for a full set.