Not everyone needs to download the full 670MB to 700MB Ubuntu ISO, thats why you can also install Ubuntu from a minimal ISO. The 14MB ISO is intended to boot the system far enough to fetch the remaining packages from the Ubuntu repositories and install the desired version. The ISO can install either Ubuntu Server, Desktop, Edubuntu, to name just a few..
X86, AMD 64 and PowerPC architectures are separated into two their own ISOs.
I have several 256MB USB flash drives that by todays standards are outdated, small size ISOs a perfect fit for them.
Using the minimal ISO has its advantages like:
- You can install either desktop or server versions of Ubuntu.
- Only the current packages are downloaded, meaning you wont have to upgrade after the installation is done.
- Due to the small size ISO it can fit inside space limited USB flash drives.