I missed the first question... my bad.
Layman's terms- RAID0 takes the data and splits it between the two drives. The speed comes because the data is written and read from both drives at the same time, halving (or close to it) the time required.
RAID1 works differently. RAID1 takes the data and writes it on two drives, using one as a copy of the other. No speed increase, but if your drive crashes you have an exact backup.