In AWS, there are 5 types of EBS storage/disk Volumes you can attach to your EC2 instance: General Puporpose SSD (API code: gp2), Provisioned IOPS SSD (API code: io1), Throughput Optimized HDD (API code: st1), COLD HDD (API code: sc1), and [...] (API code: [...] )

Magnetic (API code: standard)

^^ General Purpose SSD (gp2), is for most workloads (is default)
^^^ Provisioned IOPS (input/outputs per second) SSDS (io1), is for read/write intensive workloads, e.g. databases
^^^^ Throughput optimized HDD (st1), is for big data and data warehousing, because magnetic HDD disks are for large data sizes but slow read/write
^^^^^ Cold HDD (sc1), is for things like File Servers (less read/writes), even slower than Throughput Optimized HDD
^^^^^^ Magnetic (standard) is the slowest so is for data archiving (if you choose not use glacier)