There's a good article on Wikipedia.http://en.wikipedia.org/wiki/RAID
Raid 0 is where two or more disks work together (stripe) to do the job of one big disk. If you save a 2 bit file on a raid of 2 disks it would theoretically save 1 bit to one disk and 1 bit to the other. That way it can read and write twice as fast. However the R in RAID stands for redundant and this raid has none. If one disk fails the entire array is toast.
Raid 1 (mirror) is redundant. It is designed to guard against disk failure. A two disk Raid 1 has two identical disks doing the same job. When you save that 2 bit file it saves both bits to both drives. If one drive fails you are left with an exact copy on the other drive and no data should be lost. However, there is a 50% hit in size. ie if two 1tb disks are used to build a RAID1 the net space is 1tb.
imho since SSDs have matured there is little need for RAID in the everyday system. It should be more or less relegated to storage systems (where it was developed) such as NetworkAttachedStorage.