The redirect module is built into AWS, and is one of the simpler modules. If it is invoked, it responds with an indication that the requested argument has moved to a new URL, as indicated by its argument. For instance, if you had /strategic/environment/ as a tree of documents that you decided belonged in /vitalissues/environment/, you could notify client software of the move with the following map:
map /strategic/environment redirect /vitalissues/environment
Thus, when a client followed a link to, say /strategic/environment/wetlands/dead-ducks.html, AWS would respond indicating this had moved to /vitalissues/environment/wetlands/dead-ducks.html. An up-to-date browser will notice the redirection, and fetch the appropriate page.