What is the Bab el-Mandeb Strait that Iran has threatened to block?

The Bab el-Mandeb Strait, which Iran has threatened to block if US attacks continue, is the world's fourth largest shipping route. About 12% of the global seaborne oil passes through the strait, which connects the Red Sea and the Gulf of Aden. It is located southwest of Yemen, where the Iran-backed Houthis are based.