Short answers, pulled from the story.
Ovid wrote that the cause of his exile was carmen et error, meaning a poem and an error. The poem was the Ars Amatoria, written roughly seven years before his banishment in 8 AD. The nature of the error remains disputed; Ovid said only that it involved seeing something, and scholars have proposed explanations ranging from witnessing adultery involving members of the imperial family to involvement in political circles opposing Augustus.
Ovid was banished in 8 AD to Tomis, a remote town on the Black Sea now known as Constanta, Romania. The sentence was issued by the emperor Augustus alone, without the participation of the Senate or any Roman judge.
During his exile Ovid produced the Ibis, an elegiac curse poem written on the journey to Tomis; the Tristia, five books of elegies composed between 9 and 12 AD; and the Epistulae ex Ponto, verse letters to friends, his wife, and the emperor, with the first three books published in 13 AD and a fourth appearing between 14 and 16 AD. He may also have written the Halieutica, a fragmentary poem about fishing, though its authorship is disputed.
The reality of the exile is debated. J. J. Hartman argued early in the 20th century that Ovid never left Rome and that the exile poems are imaginative fiction. A. D. Fitton Brown made a similar case in a 1985 article, noting that no historian mentioned the exile until the 5th century except for doubtful passages in Pliny the Elder and Statius. Orthodox scholars counter that Ovid would not have left his Fasti unfinished by choice, since that poem was intended to establish his standing as an imperial poet.
The Metamorphoses and the Fasti both appear to lack a final revision, something Ovid acknowledged in the Tristia. The Fasti survives only through the first six books, covering January through June, leaving the second half of the Roman calendar unwritten. Ovid himself claimed in the Tristia that his exile prevented him from completing these works.
Latin writers who experienced exile, including Seneca and Boethius, drew on Ovid's exile works as a literary model. In the medieval period the poems shaped European conceptions of banishment and loss of place. Romantic writers later read the exile as the story of a misunderstood genius punished for artistic freedom. Modern classicists value the Tristia and Epistulae ex Ponto as primary evidence for the Roman aristocracy under Augustus and Tiberius.