A ‘genre’ is a type or style of writing – a group of texts which share similar characteristics. Contemporary examples would include novels, scientific text books, fairy tales, insurance documents, poems, tweets, and so on. There are several main genres with the Bible, including historical narrative, poetry, letters, law/instruction, and prophecy. For helpful guidance on dealing with the Bible's different genres, see Fee, Gordon D., and Stuart, Douglas K. How to Read the Bible for All Its Worth 4th ed. (Zondervan, 2014)
We're interested in the prophets here, but there isn't one single type of prophetic writing in the Bible. There are several prophetic genres, or perhaps sub-genres may be a better term. Many of these are kinds of ‘oracles’. An oracle is a distinct section or unit within the longer message – an individual prophecy within the prophetic book. In the brief summaries below, I give the basic forms of these, but of course the writers of these books used many variations on their basic themes. Sometimes a couple of the genres overlap in a single oracle or unit.
e.g. Amos 1:3 – 2:5
e.g. Ezekiel 1:1 – 3:27
e.g. Ezekiel 37:1–14
e.g. Ezekiel 4:1 – 5:17