Relegatio (or relegatio in insulam) under Roman law was the mildest form of exile, involving banishment from Rome, but not loss of citizenship, or confiscation of property. It was a sentence used for adulterers, those that committed sexual violence or manslaughter, and procurers.
A notable victim of relegatio was Ovid.
Exile or banishment is primarily penal expulsion from one's native country, and secondarily expatriation or prolonged absence from one's homeland under either the compulsion of circumstance or the rigors of some high purpose. Usually persons and peoples suffer exile, but sometimes social entities like institutions (e.g. the papacy or a government) are forced from their homeland.
In Roman law, exsilium denoted both voluntary exile and banishment as a capital punishment alternative to death. Deportation was forced exile, and entailed the lifelong loss of citizenship and property. Relegation was a milder form of deportation, which preserved the subject's citizenship and property.