Bridges use backward learning to build tables. They determine which LAN to use to reach destination X by recording the interface on which frames having source address X arrive on. The above approach works only for tree-structured topologies. That is, they are specifically excluded from the tree and do not forward packets. They are available for backup, however, should one of the other bridges or LANs fail.
Bridges periodically rebuild tables.
When a bridge or link that is part of the spanning fails, a new spanning tree is constructed. Easy to use. Just install the bridges. No software changes are needed hosts. By definition, only the bridges that belong to the spanning tree are used.