A material crime is one where the law requires a specific result, for example: Homicide. (If it is not consummated with the result of death, it will be an attempted crime)
A formal crime is one that does not require a result; an example is extortion by kidnapping, as it is not necessary for the perpetrator to obtain any result for the crime to have been committed. It is important to know that a result may exist, but the law does not wait for it to happen to consider the crime as completed. Attempt is possible in this case.
A crime of mere conduct is one that the agent commits simply by 'being' in a certain place, with trespassing being a classic example. It does not require a result. Another example is disobedience,
