The U.S. Bureau of Justice (BJS) released some statistics concerning offenders who were under some form of supervision in the adult correctional system in 2013; these numbers include people who are on probation, parole and incarcerated. There has been a slight continuous decline in these numbers. A person was on “probation” when his sentence stopped short of an “executed” prison sentence; for example, the judge might say “I sentence you to 5 years in prison. However, that sentence is “stayed” (not executed) on the condition that you….”. This means that while you may not have to go to prison (The “Big House”), you likely will have to fulfill certain conditions such as pay a fine, remain law-abiding, complete treatment (sexual, chemical, psychological, etc.), serve time in the local jail, and so forth. The length of time imposed by the judge where these conditions remain in force is known as your probationary period.
If you were sentenced to prison (not probation), you might qualify for parole from the prison facility after a portion of your sentence has been served. Again, you will be subject to certain conditions (including remaining law abiding) which are imposed by an agent of the parole board, or some similarly named agency, for some time.
Finally, if you are serving your sentence (including sentences without the possibility of parole), you are referred to (obviously) as being incarcerated and under supervision.
At the end of 2013, there were 6,899,000 people in the U.S. being supervised by adult correctional systems. 1-35 were under some form of supervision; 1-51 were under probation or parole; and, 1-110 were incarcerated in prison or local jail.