Gleason is a documentary film around the trials and tribulations of Steve Gleason, a former NFL player who retired from the game in 2008, then was diagnosed with ALS (Amyotrophic Lateral Sclerosis, aka Lou Gehrig's disease) in 2011, concurrent to learning of the pregnancy of his wife Michel with their first child. It's a disease that has no cure, and those who are afflicted by it usually die within 2-5 years after diagnosis. The sufferer's motor skills begin to erode, eventually losing them altogether, including the ability to speak without technological assistance.
Knowing that the odds for survival were bleak, and recovery completely unheard of, Gleason sets about recording his life with the assistance of a couple of associates, and begins to make video logs, while he still has a voice, imparting his philosophies on life, love, and fatherhood for his young son to watch at a day when he can understand, appreciate and take them to heart most. It's something he didn't receive as much as he would like from his own father, who worried about himself much more and expected his sons to think and act just like him, and Steve both wants (and, to some extent, internally fears) that his son will have his own mind about things.