Sounds like you might be from a Linux background ....
Volume Manager is like LVM (just better)....
Physical Volumes are like disks initialized by volume manager (you will need some label on the disk before you run vxdisksetup)
From the Physical Volumes, you create DiskGroups (like Volume Groups)
And from this, you create Volumes (like logical volumes)....
Once you get a volume, you will get a device file for this volume (/dev/vx/(r)dsk/VG_NAME/VOLUME_NAME) which you can use as you wish ... (put a new filesystem on there or use as raw)