Infamy Points are points received when you do crimes in Archeage, The number of infamy points you have decide whether or not you become a pirate.
Pirate[]
When you are a Pirate, all NPCs that are not pirate, specially guards will become hostile to you, even trying to kill you You become a pirate when you accumulate more than 3,000 Infamy points
More Info: Pirate
How to Decrease Infamy Points[]
Two NPCs in Marianople, two in Solis Headlands ,one in Sanddeep and one in Rookborne give you a quest to do public service that when completed, decrease your Infamy Points. They reduce 10, 10 and 50 infamy respectively.
Another way to decrease Criminal Points and Infamy Points is by using Draughts of Forgiveness that can be bought with 5000 Honor Points, they decrease 100 Criminal Points and Infamy Points.
And the last way to Decrease all Crime Points and Infamy points is to get an "Innocent" verdict on a Trial.