I came across this term
Alternate CD. How it different from a
Also why cant we upgrade using a live cd while we can using an alternate one as mentioned here?
The link does not specify anything about the live cd.
The alternate CD is a text-based installer and does not have a live mode. Here's where/why it's useful, according to the official download page:
Because the alternate CD contains an actual repository with the .deb packages necessary to perform an installation/upgrade (see this answer for an example/more info). The Live CD cannot be used in this manner, since it contains a compressed filesystem and not individual packages. It runs in live mode off this filesystem, and when you chose to install, it expands the filesystem onto the target hard disk.
hope that helps