dvd1
This contains everything necessary to install the base FreeBSD operating system, a collection of pre-built packages, and the documentation. It also supports booting into a "livefs" based rescue mode. This should be all you need if you can burn and use DVD-sized media.
disc1
This contains the base FreeBSD operating system and the documentation packages for CDROM-sized media. There are no other packages.
livefs
This contains support for booting into a "livefs" based rescue mode but does not support doing an install from the CD itself. It is meant to help rescue an existing system but could be used to do a network based install if necessary.
bootonly
This supports booting a machine using the CDROM drive but does not contain the support for installing FreeBSD from the CD itself. You would need to perform a network based install (e.g. from an FTP server) after booting from the CD.
memstick
This can be written to an USB memory stick (flash drive) and used to do an install on machines capable of booting off USB drives. It also supports booting into a "livefs" based rescue mode. The documentation packages are provided but no other packages.