What is the ablative absolute?

An ablative absolute is a participle phrase in the ablative case which is separate from the main construction of the sentence. e.g. agro arato, agricola domum ivit = (lit.) with the field having been ploughed, the farmer went home The ablative absolute tends to need a more idiomatic translation, for example, 'since...', 'after...', or even 'the farmer ploughed the field and then went home'