When I was in England, I heard banns read in some Churches of England. This was the practice, as Frank Gill says, of proclaiming a proposed marriage publically. If anyone had concerns or objections to the proposed marriage, they were to bring them to the priest as soon as possible. This was done 3 times before the wedding took place. There may be a few denominations in America where banns are still read, but as a general rule it's no longer a practice in America and there are many Americans who would not be familiar with the concept.
It's quite possible that different English speaking countries call a bann something different. To call it a proposal in an international community such as WikiTree will lead to confusion. To most Americans, at least, a proposal is a completely separate act that is done long before banns would ever be read. An engagement is often considered but not always considered the same act, but an engagement rarely happens in a church. Banns, to my knowledge, are always done in churches on Sunday mornings.