A collection typically contains objects that are used by the same application or are of a similar type. Collections are useful for dealing with sets of objects that are too large to be handled as a single object, but too small to warrant a separate Object storage group. For example, all objects in a collection can have the same default initial storage class and management class attributes.
You can organize objects into collections for a variety of reasons. For example, if objects related to a corporate division are kept in one Object storage group, it might be desirable to subdivide that Object storage group into collections of departmental data.