To explain the plot would be irrelevant because, without use of hyperbole, there truly is none. There is what I would call a thin strand of a narrative that connects an otherwise rambling and random series of b-roll footage. Within this strand, the distractingly inept Brad Pitt and supernaturally radiant Jessica Chastain play the world's most mismatched married couple. Dealing with the struggles of raising three boys, one of them complete with his own "Good Son-esque" story arc, they traverse all the common arguments and joys of any random married couple, but with the benefit of grating, whispery narration about absolutely nothing. I was just waiting for one of the characters to bowl us over with, "Dog, cat, red, banana, running, my Lord", a list of breathy incoherent words that would have left one half of the audience in tears and the other half fighting back fits of laughter.
The one thing I do find interesting about Tree of Life is how expertly it highlights the gap between those of us who like a good story, passable acting, and, at the very least, a script and those other folks who prefer obscure, "artistic", and revolutionary fare. For this reviewer, those three descriptive words roughly translate to "Stay, Far, Away".