What are wiki engines?

Technically speaking, a wiki is essentially a small piece of server software that allows users to freely create or edit content using any Web browser and no other special tools. The server software that is providing this capability is typically referred to as the wiki engine or the wiki software. A wiki may be developed by installing and using the wiki engine. Also a wiki farm may be created on a server or group of servers using the wiki engine for the purpose of hosting multiple wikis (sometimes called wiki instances or wiki spaces).

For more information, see
Wiki Engine List
Wiki Engine Selection