I understand the differences are subtle because a lot of the terminology overlaps, but these are two very different activities. In the article you linked to, the steps described are intended to strengthen the service NiFi is providing and the ability of users to connect. As an analogy, let's describe building a bank.
By default, the bank is built of wood, has large clear windows with no blinds, and no official sign out front. You've taped a piece of paper saying "GeoffreyBank" to the door (this is plaintext, default, unencrypted HTTP communication from your browser to http://localhost:8080/nifi).
Now, of course, you want to secure your bank. It is going to store valuable items, and people will not use it if they do not trust that you are protecting their property. So, you build stronger walls and put an inner office so that their transactions cannot simply be observed by anyone on the street and you have professional signage so they can recognize that it is the correct bank.
This is analogous to