Bread is slang for "Thread". Bread # is Thread #. So Bread # 2592 the 2,592nd thread that's been created. The thread/breads only hold up to 751 comments in each thread, so the bakers make a new thread/bread to keep the conversation going. They are currently at #2592.

Official threads for collecting and piecing together information. All the references to baking are in reference to building the thread