What are dofollow and nofollow links?

A dofollow link is any link that a crawler bot is able to follow.  A nofollow is the opposite.  How can you tell the difference?  Here’s an example of a dofollow link <a href=”https://tagteamdesign.com”>Tag Team Design</a>
Here’s an example of a nofollow link:  <a href=”https://tagteamdesign.com” rel=”nofollow”>Tag Team Design</a>