title: What is the difference between an Index and a Foreign Key?
body: <p>I want to create a database with 3 tables. One for posts and one for tags and one that links posts to tags with the post_id and tag_id functioning as foreign key references.</p>
  
  <p>Can you explain what an Index would be in this scenario and how it differs from a Foreign Key and how that impacts my database design?</p>