Short answers, pulled from the story.
A knarr was a Norse merchant and cargo ship used during the Viking Age for transporting goods such as walrus ivory, wool, timber, wheat, furs, weapons, livestock, and slaves. It crossed the North Atlantic to supply settlements in Iceland, Greenland, and Vinland, and was also used along trade routes through the Baltic, Mediterranean, and other seas.
A knarr was approximately 16 meters, or 53 feet, long and could carry up to 30 tons, or about 60,000 pounds, of cargo. It required a crew of as few as six people to operate, making it an efficient vessel for long ocean voyages.
The knarr was wider, deeper, and shorter than a longship. It was designed as a cargo vessel built for carrying goods and livestock across rough ocean waters, while the longship was built for speed and used primarily as a warship. The knarr could carry more cargo and be operated by a much smaller crew.
Skuldelev 1 is the first physical specimen of a knarr ever identified, discovered during a 1962 excavation at Skuldelev, Denmark. Archaeologists found five Viking ships deliberately sunk with rocks around the 11th century to block a passageway. Skuldelev 1 measured about 16 meters long and could carry upwards of 30 tons; it is now housed in the Viking Ship Museum in Roskilde, Denmark.
Historical and archaeological evidence strongly supports that knarrs were used to reach Vinland, now known as Newfoundland. In 1960, explorer Helge Ingstad and archaeologist Anne Stine Ingstad discovered a Viking settlement at L'Anse aux Meadows in Newfoundland, confirming that Norse voyagers crossed the North Atlantic to North America. The knarr's cargo capacity made it the practical vessel for supplying such distant settlements.
W. Hodding Carter IV had a knarr reconstructed in 1997 based on historical designs and sailed it from Greenland to Newfoundland in 1998 with a crew of nine. The voyage revealed that the traditional steering oar had to be modified by reinforcing the hull attachment and tuning the balance to make the vessel controllable. The reconstructed ship is now housed in a shed in Norstead.