RAID 0 does what is called "striping". This means it writes part of a file to one drive and part of the file to another. This is done because it is faster to write half of a file to two drives at the same time then all of the file to one. You can also read it twice as fast. RAID 0 is done for speed.
RAID 1 is where the whole file is written to one drive and an exact copy is written to the other drive at the same time. This is done for safety as one drive can died and the files are still available on the other drive.
Back to RAID 0 and you can see the problem, as if one drive dies you are only left with half of every file and no way to determine what the other half should look like.
HOWEVER, RAID 0 is no more risky than have one large drive with everything on it. In either case, if one drive dies, you lose everything.
I find that StorageReview.com site has the best textual description of RAID
and AN&NC has the best animations explaining RAID
Since laptop hard drives are (usually) slower speeds (to save battery power and run cooler), having a RAID 0 will speed things up. And then you should do regular backups to a large external HDD.