Explanation

Autocorrection

It is also known as text replacement, is an automatic data validation function used in word processors and text editing interfaces

AutoFormat 

This feature automatically formats a document as you type it by applying the associated styles to text

Auto format feature is used to replace straight quotes with smart quotes while typing

Smart Tags

It is used for creating actions associated with words or phrases in Microsoft Word, Microsoft Excel, and Internet Explorer 6. For example, when Smart Tags are enabled in a document, Word may recognize certain phrases (such as names or dates). Smart tags are no longer is in use.