The Northwest passage was a route from North America to Asia. Asia had many items, such as spices and silk that were desirable to Europeans. They were also interested in finding gold.
Kings were seeking route that went around America, in the north and west direction. Primarily, the Spanish, French and English were trying to find the fasted route before each other did, causing attacks and pillaging of each other's ships.
In the 1500 and 1600's, there were several explorations undertaken, in an effort to find the fasted passage to Asia. However, explorers found the extremely dangerous and the climate harsh. Dangers included freezing temperatures, shallow waters, islands, thick ice and gigantic icebergs.