The term for continuous daylight at the Arctic Circle during the summer solstice is the midnight sun.
The midnight sun occurs because Earth’s rotational axis is tilted by about 23.4 degrees. During the Northern Hemisphere’s summer, the Arctic is tilted toward the Sun, allowing the Sun to remain above the horizon for 24 hours or more. At the Arctic Circle itself, the phenomenon is associated with the June solstice; farther north, it lasts for much longer.
The midnight sun is also called polar day and has a southern counterpart south of the Antarctic Circle during the Southern Hemisphere’s summer. At the North Pole, the Sun remains above the horizon for roughly six months, although atmospheric refraction and the Sun’s visible disk affect the exact dates.
“White nights” describes twilight or very bright nights when the Sun remains below the horizon, so it is not the same phenomenon. Aurora borealis is caused by charged particles interacting with the atmosphere, while polar night is the winter opposite of the midnight sun.