Smart Tags are like helpful assistants for your computer. They help you do things quickly and easily, without having to type a lot of words or click a lot of buttons.
For example, let's say you are reading an article on the internet about a new book. The Smart Tag might notice that the book's title is mentioned in the article, and offer to help you learn more about the book. If you click on the Smart Tag, it will give you options like looking up the book on Amazon, adding it to your wishlist, or finding reviews of the book.
Another example is in Microsoft Word, where Smart Tags can be used to correct spelling mistakes or offer synonyms for a word you're writing. If you type in "recieve" instead of "receive," the Smart Tag will pop up and suggest that you change it to the correct spelling.
In short, Smart Tags are little helpers in your computer that make your life easier by offering suggestions or helping you get things done faster.