Below is a simple diagram that depicts the types of storage:
NAS - Network Area Network:
In file storage - NAS -, the computation overhead is embedded within the storage, more resources are consumed by the storage.
It makes this solution slower than object storage for example.
File storage architecture is simple and it depends on a hierarchy in the form of directories and subdirectories. CIFS/NFS represent examples of the file storage technology.
SAN - Storage Area Network:
In block storage - SAN - the computation overhead lies with the client host and is separated from the storage. Block storage is organized in logical units called LUNs.
Block storage is faster because there is no computation overhead tied to the storage.
Fiber Channel and iSCSI are examples of these technologies.
In the cloud, we have AWS Elastic Block store (EBS) for example that provides a virtual SAN with volume management provisioning for databases or VMs.
In object storage the data is stored as objects identified by a unique identifiers. Objects has metadata which allows for indexing and management of the data that is stored as objects.
AWS S3 or Microsoft Azure Blob Storage - ABS - are examples of the object storage type. Object storage is good for storing cold data, archiving, backup, and managing large volumes of unstructured data. There is no hierarchy in object storage, data is stored in a flat structure called buckets. Object storage is flexible enough to store different type of data.