What the North Node is
The Moon’s orbit is tilted about five degrees against the path the Sun appears to follow through the zodiac. The two orbits cross at two points, called the lunar nodes. The North Node is where the Moon crosses heading north, and the South Node is exactly opposite. Eclipses can only happen when a New or Full Moon falls close to one of these points.
The nodes drift backward through the zodiac, spending about 18 to 19 months in each sign and returning to the same place every 18.6 years. Today the North Node is at 29°08′ Aquarius.
What it means in astrology
Astrologers read the nodes as a pair. The South Node points to what comes easily: habits, talents and comfort zones you fall back on. The North Node points to the qualities you are meant to grow into, which usually feel less natural at first. In Vedic astrology the same points are called Rahu (North) and Ketu (South).
The sign of your North Node describes the kind of growth; its house, which needs an exact birth time and place, shows the area of life where it plays out.
True node or mean node
The real lunar orbit is pulled around by the Sun, so the true node swings up to about two degrees either side of its average position. The mean node smooths that wobble out. The calculator uses the true node by default and tells you if the mean node would put yours in a different sign.