Page views correlate to any web pages viewed, which includes landing pages and tripwire pages. These page views can be from any source and do not necessarily have to come from a link you sent out. For example: A user opens a landing page and copies the URL to forward to his friend. When that URL is opened it will not register as a link click but will show a page view.
Link clicks correlate to social media clicks and email clicks. These clicks are generally unique per user and help identify how many people interacted with the social media postings or links in your email campaigns. Also, note that a link click is measured when the link is clicked and is not dependent on the landing page loading.
Clicking the "unsubscribe" button on an email is not considered a link click.