Logical Volume Management is a powerful way of managing disk data. LVM enables you to move data between disks, add or remove disks, change volume sizes, and make frozen snapshots of data while your system is running. Any Fedora system administrator should be learn the command-line tools used to administer LVM, because they're essential if you need to perform system recovery work or remote storage adminisitration.
System-config-lvm provides a graphical interface to the LVM tools (and related utilities, including fsck and resize2fs) which is good for non-emergency storage administration. It enables you to manage your logical volume and filesystem configuration with a few mouse clicks, and it prevents potentially-disasterous command-line mistakes such as reducing a logical volume size before reducing the filesystem contained within that volume.
(One word of warning: system-config-lvm does not recognize RAID elements as being in use, and therefore lists them as "Unitnitialized Entities". If you are using a LVM-on-RAID configuration, system-config-lvm will let you wipe out RAID elements by making them into PVs. Be careful!)
Nearly an informational only tool. Only nice to automatically size and resize lv's once created. Can't get away from the CLI lvm shell and individual cmdlets to manage any aspects of physical volumes and volume groups.
CLI management application for snapshots, PV and VG configuration, Raid, etc is sorely needed to prevent the CLI runaround and provide visual verification, "are you sure" confirmation and config rollback abilities.