In the Bucket Explorer, Buckets are classified in two types :

Buckets

These are the simple buckets created by you and are used by you only. These are viewed accessed and manipulated by you (owner) only. These buckets are listed with simple folder icon as seen on windows operating system.

Shared Buckets

Buckets owned by you - These buckets are created and owned by you and you want others to see them as well. Your guests can have privileges over these buckets as defined by you. A different icon is displayed for these Buckets.

Buckets owned by others - As title suggests, such Buckets are owned by some one else and you are permitted to view/manipulate them. Similar to Buckets owned by you, permissions you have are right concern of their respective owner(s).