Bucket policies provide centralized, access control to buckets and objects based on a variety of conditions, including Amazon S3 operations, requesters, resources, and aspects of the request (e.g., IP address). The policies are expressed in our access policy language and enable centralized management of permissions. The permissions attached to a bucket apply to all of the objects in that bucket.
Individuals as well as companies can use bucket policies. When companies register with Amazon S3 they create an account. Thereafter, the company becomes synonymous with the account. Accounts are financially responsible for the Amazon resources they (and their employees) create. Accounts have the power to grant bucket policy permissions and assign employees permissions based on a variety of conditions. For example, an account could create a policy that gives a user write access: