An infraction is sort of like a warning for an offence such as flame baiting (e.g: saying you hate misty in the misty fan club like i did...>.<) Posting inapropriate picturtes (not guilty of that thank goodness) and breaking the forum rules (not typing enough, hacking or messing up the commmunity and so o)n.
With some warnings you will get points depending on how serious your offence is and how often you offened. I have had 3 warnings which have now expired but I have 2 points which I think dont expire. I have heard if you get 10 points you get banned permenatly (not good).
So try not to get infractions if you can and be careful what you say in certain places (Belive me, dont say you hate misty in the misty fan club, you would not belive the amount of hate mail you get lol :) I thought it was kind of funny)