You can win, collect or buy cards in several ways. You can find a list ways how to get cards here.

However, you can redeem cards to gain several stats:

Card Info
Name	AA
Effect	DMG
Amount	50
Permanent	Yes

Card Info
Name	ChatTDT
Effect	Range
Amount	0.001
Permanent	Yes

Card Info
Name	AA Logo
Effect	Gold
Amount	50M
Permanent	No

Card Info
Name	AA Tunnel
Effect	Gem
Amount	25K
Permanent	No

To get there cards, you have to collect or buy cardsets.

Here you will finde some information about the cards and the card system