Hi, lovinlettuce, and welcome to Chowhound! When you post, you have a couple of hours to edit your original post by clicking on the "edit" button in the lower right below your post. After that, you can reply to your original post if you want to clarify or correct something.
The posts stay up permanently because they add valuable info for anyone searching on the posted topic. No need to delete, because it's very likely that someone else will search the board and come across this thread.
Posts that are off-topic or that are deemed inappropriate by the moderators are sometimes deleted.