Organized crime is just what the name suggests: there is some sort of organization behind it. When you think of organized crime, it is best to think of a hierarchy existing behind it. This might take the form of a gang, a cartel, the mafia, or any other criminal organization. There are often decision makers who plan the criminal activities and profit the most from them. Then there are the people who carry out or execute these crimes. Some crime syndicates have very complex hierarchies with several levels of middle management and diversification of roles, the same way a large corporation would. Others are more based around the relationship between a patron and a client. Others are centered around certain families and neighborhoods or geographical locations. The motive of most organized criminal organizations is usually monetary profit (terrorist groups being a notable exception). This is usually achieved through methods such as extortion, embezzlement, racketeering, illegal gambling, or even theft. Different forms of organized crime can be found all over the world and in nearly every society.
Unorganized crime, by contrast, lacks any hierarchical system. This refers to any crime that is not committed by a criminal organization. This type of criminal behavior can include pretty much anything and happen for nearly any motive. These crimes are usually committed by an individual for personal reasons. Sometimes they are planned in advance, but that does not necessarily need to be the case.