Jonah is the 32nd Book of the Bible. It is preceded by Obadiah and followed by Micah. Jonah is also a character in the Bible, and since the book is specifically about him, we will refer to both of them on this page.
Jonah's duty was to be a prophet to the Northern Kingdom of Israel in around 8th century BC.
As a prophet, it was his duty to hear from God and act upon what God told him to do. Often, God told him to preach to various people and Jonah, of course, did what he was supposed to do. That is, until God told him to preach to the city of Ninevah telling them of their impending doom. You see, Ninevah was a very sinful city and did not take kindly to people telling them what to do.
Jonah was terrified by Ninevah, so instead of heading straight there he decided to flee. He ended up hitching a ride with some sailors who ended up in a terrible storm in the middle of a sea. They decided that the storm was from the wrath of God, and they decided to throw Jonah overboard. Immediately the storm ceased, but Jonah was swallowed by a fish.
Jonah ended up being spat back on shore by the fish in one piece, and was so moved by the experience that he decided to go straight to Ninevah and preach about their impending doom.
When he got there and started preaching, they weren't angry at Jonah. Worse, the people of Ninevah were humbled and began to repent and change their ways.
In the end, God decided not to allow Ninevah to be destroyed which angered Jonah greatly. God made a plant grow over Jonah's shelter in the desert to give him shade, then caused the plant to wither as a result of Jonah's anger.