Re: dynamic hard drives
You can use RAID to create a variety of different hard disk arrays with varying number of disks. So for example, with 2 disks you can create a RAID 0, where data is striped across both drives, and the operating sees them as 1 "Dynamic" disk.
Or you could create a RAID 1, where the data on two drives are mirrored in real time. Once again, the operating system would see this as a single drive. This creates redundancy in case one of the drives were to fail.
Raid can be achieved different ways. You have hardware raid, where the configuration and functionality of RAID is controlled by a hardware raid card, usually it plugs into a PCI slot on your motherboad.
Or, you might have Software RAID. In this arrangement, all of your drives are simply connected to the motherboard as normal, and a software program or operating system boots and controls your RAID setup for you. If you have something like a Synology NAS, or a FreeNAS server, this is software raid.
Many consumer grade motherboards also offer some sort of onboard RAID controller. There is controversy over this though. Hardcore RAID users will advise against using onboard raid.
Personally, I have an LSI RAID card that I use to control 4 drives in a RAID 10 arrangement. The card plugs into my motherboard and the drives plug into the card. I have a fault tolerance of 2 drives, so if 2 drives fail, I my data is still readable.
Check the Wikipedia page on RAID for more info. If you are thinking of configuring a raid setup on your computer, post your specs and we can help you do that.