One common characteristic of organized crime, is that it usually specializes in crimes that are made so by government. For example if a law is passed against making and selling alcohol, all of the law-abiding businessmen will stop, but people will still want alcohol, so criminals form an organization to furnish the alcohol. Because of the government law, the criminal enterprise has less competition and can sell at a higher price (where else can the public get their alcohol?), and because they are criminals, they are willing to threaten or kill other criminals who try to enter their business.
To expand on the previous answer, organized crime has a boss, captains, lieutenants, or something equivalent in terms of rank and power. In terms of the types of crimes they commit, they are much more often something like gambling, racketeering, smuggling, etc. as opposed to single acts of thievery like bank robbery. They create criminal enterprises instead, that aim to make money over time with a series of illegal operations. Organized crime is also much more likely to have assets in legitimate banks and own property and front companies than small gangs of criminals or individuals would.
This is one reason the FBI often focuses a task force on organized crime - to try and take down a network of criminals is a much more efficient and effective way of fighting crime. The problem is you usually have more talented criminals to contend with.
It is not clear which facts you want, so it is hard to know if this is the answer you want.
Basically, organized crime cannot be exactly defined. Basically, the idea is that organized crime is crime that is done by a group of people that is highly organized, as opposed to some guy going off by himself and robbing a bank, for example. The FBI defines organized crime like this:
The FBI defines a criminal enterprise as a group of individuals with an identified hierarchy, or comparable structure, engaged in significant criminal activity.
But how do you know if some group has an "identified hierarchy" or is "engaged in significant criminal activity?" This means that there are gray areas as to where organized crime begins and a bunch of thugs who hang out together ends.