There is a very nice article about the aforementioned topic. The following URL provides the pages to the article, with some nice illustrations.

http://serverlinux.blogspot.com/2007/12/introduction-to-lvm-with-rhel-fe...

Here in part is some of the article text.
Introduction to LVM with RHEL, Fedora or Centos Linux
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This is the first part of an overview of Logical Volume Management. LVM was written originally by Heinz Mauelshagen in 1988. LVM has the advantages:
* Resizing of logical groups
* Resizing of logical volumes
* Snapshots from Read/Write volumes (in lvm2)
* Raid 0 of Logical Volumes. In this example i will create physical volumes (in /dev/sdb), a logical group and then a logical volume inside the logical group.
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The author is
Walter Lamagna
University Student (Engineering), Sr. Unix Administrator, www.walterlamagna.com.ar