What does "LiveCD" mean?

From What is LiveCD? - Computer Hope:

The name of compact discs that contain an operating system and often other programs. LiveCDs are capable of running on the computer without having to be installed and hard drive storage space is not required. These CDs are also a way for users to try an operating system without having to format their hard drive and install it. For example, many Linux distributions are available in LiveCD format allowing Microsoft Windows users to experiment with Linux without having to erase Windows.

Many LiveCDs are saved as an ISO image, allowing a user to create a CD directly from the ISO without having to set up the CD manually. An example of a LiveCD is the Anonym.OS LiveCD, an OpenBSD OS designed to help keep the user anonymous on a network and the Internet.

And no, ubuntu-20.04.2.0-desktop-amd64.iso isn't a LiveCD until you make it a LiveCD.

Most Ubuntu media is live, ie. bootable and usable on it's own, allowing you to try before install. There are exceptions though (that aren't EOL or end-of-life yet)

Default installers

• ubiquity (desktop),
• calamares (some desktop flavors),
• subiquity (server)

all run on live media; though some older ISOs still use the di (debian installer) which is not a live system.

Lubuntu for example used the di installer on alternate media so it could be used to install on machines with <768MB of RAM (too little to use live and installer at the same time). Non live media though is mostly EOL (eg. Lubuntu no longer supports 18.04 which was the last release that provided non-live media)

LiveCD - this means that this disk contains an OS or a program that can be run from the disk itself, without having to install it on another media