A Value is the top-level representation of data in Slate, containing both a Document and a Selection. It's what you need to pass into the Slate <Editor> to render something onto the page.
Get a subset of the Marks that are present in all the characters in the current selection. It can be used to determine the active/inactive state of toolbar buttons corresponding to marks, based on the usual rich text editing conventions.
blocks
List
Get a list of the lowest-depth Block nodes in the current selection.