To the page : The object keeps the same position in relation to the margins of the page. It will not move even if you add or delete text or other objects such as images.
To the paragraph : The object is associated with a paragraph and moves with it. It can be placed in the margin or in another location.
To character : The object is associated with a character but is not a text sequence. It moves with the paragraph and can be placed in the margin or somewhere else (this method is similar to anchoring to the paragraph but cannot be used with drawing objects).
As character : The object is placed in the document like any other character affecting "text line height and line feed".