kernel: The kernel is the core or nucleus of an operating system. Basically, it provides a way for software and other parts of the operating system to communicate with a computer's hardware .
Distribution: An operating system based around Linus Torvalds' Linux kernel. They come in all "shapes and sizes". Many are meant to be installed and be used by professionals on public Internet servers or on graphics rendering farms and other environments. Others are meant to be installed by the general public as an alternative to proprietary operating systems. Each distribution reflects either the needs of its target market, in the case of the commercial distributions or the wishes of its developers, as is the case with distributions created by individuals or non-profit organizations.
ISO images: This is a set of packaged programs created to be eventually burned to (i.e. copied to) CDs. A Linux distribution (see above) can be obtained by downloading the ISO images offered by companies and organizations and burning them to CDs.
