Every year Billions of dollars are lost on chargebacks and fraud. Some companies go out of business not because they have a bad product or do not market themselves, but because of fraud.
Organized Fraud is a form of organized crime. The criminals use identity theft or some other means to apply for valid credit cards under someone else's name. Once issued, they set up a drop location where they have goods delivered to (usually a vacant house or apartment) and they spend the cards up to their limit. When the bill comes 30 - 45 days later, there's nobody there to pay it and the criminals move on to another credit card...
A minor variation on this theme is the hacker/cracker using software to generate seemingly valid credit card numbers. Both types of criminals are normally looking for items that can be easily converted into cash. These are probably the hardest criminals to catch because they know all the ins and outs of the system and are constantly altering their techniques as soon as an anti-fraud measure begins to show any level of success.
Opportunistic Fraud is, quite simply, fraud that is committed because the opportunity happens to present itself. Perhaps a waiter, a little short on cash, copies down the credit card info from a customer and then goes online and buys his wife a nice birthday present. There are a million variations on this but essentially, the person committing fraud doesn't normally do this for a living. They are amateurs who happened to take advantage of an opportunity.
Cardholder Fraud is when the legitimate cardholder is the person committing fraud. Sometimes they claim they never received the merchandise. Sometimes they claim they never ordered the merchandise. Whatever the excuse, the cardholder knows how card not present transactions are treated by the credit card companies and aims to take advantage of the system. Even if the merchant calls the customer and confirms that they placed the order, when the bill comes they can claim they never heard of the company and the credit card company will stick the merchant with the liability. A minor variation on this type of fraud which I still consider Cardholder Fraud is the spouse or children who use the card and then deny.