Hi David and welcome to SevenForums,
RAID stands for Redundant Array of Independant Disks. In laymans terms, its a way of "connecting" two or more disks to improve performance.
For example, a RAID0 "combines" two or more disks such that they appear to be a single disk only. Data is written across both disks, resulting in improved performance when compared to only a single disk. RAID0 is actually not redundant since if a single disk fails then all data written across both disks is lost - it a high risk strategy.
In a RAID1, data is written to both disks at the same time - think of it as a sort of backup. The two disks are mirrored images of one another. There are variants of RAID1 called RAID5 and RAID10, which are popular with data storage centres (the SevenForums database uses a RAID10 if I'm not mistaken).
RAID's have laregely become redundant (excuse the pun) with the advent of SSD's and cheap external USB backup devices. So, for the average person/user, RAID really holds no benefits. In specialist environments RAID's are still very good - I use them myself, as ou get both speed and larger storage volume, but again, this is a specialist environment.
In your case, you wouldn't RAID your SSD and HDD together, since the resultant RAID0 would only be 64GB in size (the remaining space is unusable and the system cannot access it).
You can happily install your program files to the SSD, but keep data files and media on your HDD - you will still get very good performance that way.
Regards,
Golden