Although I've already provided a couple topics on my pfSense firewall, I want to backtrack into the basics to qualify what pfSense is able to do, what it is, and how it is put to work. What is a better way than to have someone else do it for me? Mark Furneaux has done a series of pfSense videos on YouTube which I will link here, but make sure you 'like' them on his channel if you find them informative.
The videos are titled as pfSense 2.3, which wasn't released when he started the series but is now. All of the concepts he discusses also apply to earlier versions of pfSense, but a correction he may not have known of when he did the video is the release of an update of FreeBSD 10.3, the foundation that pfSense 2.3 runs on. Just as I did with that explanation, these blog entries will discuss relevant sections of Mark's videos I have found helpful, or I may add other material to what he has.
Without further delay, here is the first part of his series, this episode titled "The What and Why of pfSense":