"Warcraft III: The Frozen Throne" is an expansion of "Warcraft III: Reign of Chaos," both of which can be purchased together as a digital download on the Blizzard Entertainment website for $9.99, as of 2015. A hard copy of the TFT is available on Amazon.com for between $5 and $10.
"Warcraft III" is a real-time strategy computer game created by Blizzard Entertainment. "Reign of Chaos" was release in July 2002, and "The Frozen Throne" was released in July 2003. TFT requires ROC to play. TFT expands ROC by adding new units for each race, two new auxiliary races, four campaigns and five heroes.