In a block storage, files are split into evenly sized blocks of data, each with an own address, but with no additional info to provide more context for what that block of data is.
Object storage is quite different from block storage. Instead, the entire clumps of data are stored, in an object which contains the data, metadata and a unique identifier. In this arrangement, there is no limit on the type or amount of metadata, which makes object storage powerful and customizable. Metadata can include anything from the security classification of the file within the object to the importance of the application associated with the info.
In the world of enterprise data centers, object storage is used for these same types of storage needs, where the data needs to be highly available and highly durable. For instance, those who have used facebook for storing or sharing images have used object storage without their knowledge.
However, object storage generally doesn’t provide the user the ability to incrementally edit one part of the file. Objects have to be manipulated as a whole unit, requiring the entire object to be accessed, updated, then re-written in their entirety.
Another key difference is that block storage can be directly accessed by the operating system as a mounted drive volume. And object storage cannot do so without significant degradation to performance.