Redundant Array of Independent Drives or Redundant Array of Inexpensive Drives also known as RAID is a way to create a sub-storage system comprising several individual discs.
RAID-0 "Stripe" is the level of RAID technique used to improve read and write performance compared to using a single drive. In this configuration the data is subdivided into segments and these segments are written to alternate drives.
As an example Drive 1 will get the first block of data, Drive 2 will get the second block of data. If there are only two drives in the array the next block of data will get written to the first drive and so on. This means that the read and write performance of the array is typically somewhere near the combined total throughput of both drives but there is a higher risk of catastrophic data loss due to the fact that data is now spread across two disks. As such if one disk fails then the other disk contains only half the required data and recovery is impossible.
This is in contrast with RAID-1 "Mirror" arrays where, due to the data being copied to two drives instead of one, the reliability is increased due to both drives being identical (if one drive fails you still have your data) but there is no performance increase.