"Ports" refers to a system for managing third-party software, inherited from FreeBSD, typically located in /usr/ports/(categoryname)/(portname). The port itself for any given package does not contain the actual software it installs, but rather instructions for automatic download and installation. A "package", on the other hand, contains the compiled software along with a scripted installation method. The end result for either format is the same, and software installed via a port can be manipulated using package tools, and so on.
dfports is the DragonFly-specific overrides to the FreeBSD ports system. As the DragonFly system changes from its FreeBSD-4 roots, some ports may not install correctly. dfports corrects for these differences. Each directory in dfports corresponds to a directory that already exists in ports. In general, it's safe to install from a port unless a override exists.
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