A detention and an arrest are very different from one another legally. The subject often has one of three options during and after a police interaction: (1) investigative detention; (2) an arrest; or (3) neither detention nor arrest, in which case he or she is free to depart.
Investigative detention in common law simply refers to a way of keeping someone while a questionable circumstance is being investigated. Detention may be regarded as an arrest if it lasts longer than a predetermined period of time.
Most arrests are done in accordance with the legal provisions provided in Title 18 of the United States Code and its supplemental provisions, under which a person may be detained for a protracted amount of time (longer than detention),
be driven to the police station or another place (subject to the right to an attorney) and be prepared to appear in court for a bail hearing.
Police encounters don’t always end in “arrest vs. detain.” Even if you are under no need to respond to the questions the police officer asks, you have the right to do so. It can just be a simple traffic infraction for a car. However, it can be called detention if a person honestly feels unable to go.