TheOneRing.net reports that it has heard from multiple sources that the Lord of the Rings television series will be focused on young Aragorn.
If you need a refresher, Aragorn is the character played by Viggo Mortensen in the Lord of the Rings film trilogy. Aragorn is the last of the line of kings of Gondor. However, he lived in exile among the Dunedain rangers for years, leaving Gondor to be ruled by its stewards in his stead. The third film's title, The Return of the King, takes its name from Aragorn's return to Gondor to reclaim his throne and usher in a new age for Middle-earth after Sauron's defeat.
It's not entirely clear what "young" means in the context of "young Aragorn." In The Two Towers, Aragorn tells Eowyn that he is 87 years old, which is old by human standards, but young by the standards of the Dunedain, who can live to be over 250 years old. "Young" seems like a relative term.
The story of young Aragorn may even have been foreshadowed in the prequel film The Hobbit: The Battle of the Five Armies. As TheOneRing points out, the elven king Thranduil tells his son, Legolas, about someone he must meet, saying that "his father Arathorn was a good man and his son might grow to be a great one."
This mention breaks continuity with the books somewhat - Aragorn wasn't born yet when the events of The Hobbit took place, based on the timeline of JRR Tolkien's original novels - but it is a clearly a reference to Aragorn, whom Legolas was already familiar with when the two heroes attended Elrond's council in Rivendell in The Fellowship of the Ring. This is just speculation, but perhaps the television series could cover how Aragorn and Legolas meet each other for the first time.
All that has been officially said about Amazon's Lord of the Ring series is that it will not actually retell the story of The Lord of the Rings, but be set prior to those events. The Lord of the Rings series is also said to be set to become the most expensive television series ever produced. Peter Jackson, the director of The Lord of the Rings movies, may be involved in a producing role.