There are currently at least three bootable media images available for download on www.gentoo.org: the Minimal Installation CD, the Admin CD, and the LiveGUI ISO. These image files may be written to media in order to boot a physical machine, or used to boot a virtual machine.
The bootable media can be used to install Gentoo.
Minimal Installation CD
The minimal Installation CD provides a very light CLI environment which may be used for Gentoo installation. Note that the emerge command is not available.
The downloaded file will have a name along the lines install-amd64-minimal-20220130T170547Z.iso.
A hardened version of the Minimal Installation CD with some additional packages to support advanced installs, recovery diagnostics of existing installs, perform additional hardware testing, and provide a better value to users wishing to utilize the full 700MB of CD-R capacity. Additional included packages can be seen in this diff: minimal/admincd diff
Writable directly to a USB stick or a dual-layer DVD, this amd64 image boots into KDE Plasma and is supplied with many useful packages such as office applications, Internet suite, graphics tools, system administration packages etc.
The LiveGUI can be useful for system maintenance, and is designed to show off what a full Gentoo installation can look like.
The list of packages included is found in the catalyst specification file. Portage may be used to install more packages, but changes aren't persistent.
See the release announcement for more information.