Amazon S3 is designed to store objects. All objects are stored in buckets and consist of a:
Value—Is the content that you are storing
The object value can be any sequence of bytes but must be smaller than five gigabytes. There is no fixed limit to the number of objects you can store in a bucket. Almost all objects have values; the single exception is a Delete Marker. For more information, see Delete Marker.
Key—Is the handle that you assign to an object that allows you retrieve it later
For more information, see Keys.
Metadata—Is a set of key-value pairs with which you can store information regarding the object
For more information, see Metadata.
Access Control Policy—Is the access control policy controls access to the object
For more information, see Access Control Policy.
Version ID—Is a string generated by Amazon S3 when you add an object to a bucket
Within a bucket, a key and version ID uniquely identify an object. Amazon S3
gives objects unique version IDs when they're added to a versioning-enabled bucket,
and null when added to a versioning-suspended bucket. Objects in
unversioned buckets also have a version ID of null. For more
information, see Versions.