Simple spaces are designed for increased performance, but don't protect your files from drive failure by keeping multiple copies. They're best for temporary data (such as video rendering files), image editor scratch files, and intermediary compiler object files. Simple spaces require at least one drive.
Mirror spaces are designed for increased performance and protect your files from drive failure by keeping more than one copy. Two-way mirror spaces make two copies of your files and can tolerate one drive failure, while three-way mirror spaces can tolerate two drive failures. They're good for storing a broad range of data, from a general-purpose file share to a VHD library. When a mirror space is formatted with the Resilient File System (ReFS), Windows will automatically maintain your data integrity, which makes your files even more resilient to drive failure. Two-way mirror spaces require at least two drives, and three-way mirror spaces require at least five.
Parity spaces are designed for storage efficiency and protect your files from drive failure by keeping more than one copy. Parity spaces are best for archival data and streaming media, like music and videos. This storage layout requires at least three drives to protect you from a single drive failure and at least seven drives to protect you from two drive failures.