An object is any item you place on a page in your book. Photos, widgets (interactive media), shapes, text boxes, tables, and charts are examples of objects.
There are three kinds of objects:
An inline object is embedded in the text flow and moves with the text.
A floating object is fixed to a particular position on a page. You can drag floating objects anywhere on a page, wrap text around them, or layer text or other objects over or behind them.
An anchored object is fixed to a particular position on a page, but it’s also attached to specific text (a word or paragraph, for example). If the text moves to another page, the object appears on the new page in the same position. An anchor marker 
indicates the text the object is attached to; you can drag the object or the marker anywhere on the page.
The objects you can add to a book and the way they appear depends on the kind of template you’re using.
Landscape: You can add any kind of object anywhere in a landscape template. When the reader switches to scrolling view in a landscape template, floating and anchored objects are hidden. However, if you give an object a title or caption, or enable the object to be viewed larger, the object appears in scrolling view as a thumbnail image, which the reader can tap or click to maximize the object.
Portrait: You can add any kind of object to a portrait template, and the objects always appear.
EPUB: In the body pages of an EPUB template, you can add tables and images, as well as gallery widgets, media widgets, popover widgets, and HTML widgets. When you insert a popover widget, table, or image, it’s placed inline. When you insert a gallery widget, media widget, or HTML widget, it’s anchored. On the title page or in the table of contents in an EPUB template, you can add any kind of object—except widgets.
In landscape and portrait templates, you can change an object from one kind to another. You can’t change an object to a different type in an EPUB template.