[dba-Tech] RAID Drives

Can anyone give me a thumbnail education on RAID drives? In my specific
case, I have an old server with 5 visible drives in a RAID. From Win
Explorer I can see 2 drives, C:\ and D:\. I don't think there are any
hidden drives on the box. Are C:\ and D:\ partitions on these 5 drives?

If I understand RAID correctly (and I freely admit that I'm seriously
ignorant here), each file-save operation writes one fifth of the data to
each drive, plus redundant data (somewhere), so that if any given drive
goes down, the data on it is also elsewhere, enabling me to replace said
drive without even powering down. Is that part correct, at least?

Now for the serious question. Accepted wisdom says that the optimal SQL
installation puts the data on one drive and the indexes on another, with
(if possible) SQL itself on a third drive. 

Is this correct? Given a RAID setup as described above, how would I do
this? Should I reformat the RAID and create several drives? If I did
that, then I could easily move the indexes to some other drive, but am I
actually gaining something by doing this? Or is this all hocus-pocus
along the lines of multiple partitions on one hard disk?

Remember, as you read this, that there are no stupid questions -- only
stupid people :)

Arthur