FreeBSD than in Linux. In Linux, IDE devices are hda, hdb, etc, and SCSI devices are sda, sdb, etc. Instead of partitions, there are slices on each disk, such as da0a, da0b, etc. Each slice has partitions, so you can have something like da0e1. I have no idea how this stuff works, so if anyone feels like reading the FreeBSD handbook and figuring it out, feel free.
Device names can have prefixes, too.
Technically speaking, you can have rda0, but we don't. This directory contains various software that can be downloaded and installed. To install anything, you can cd into it, and run make install . This will automatically download any packages you need, compile them, and install them. You can also update the ports tree using cvs.