Lunar node

A lunar node is either of the two orbital nodes of the Moon; that is, the two points at which the orbit of the Moon intersects the orbit of Earth (the ecliptic). The ascending or north node is where the Moon moves into the northern ecliptic hemisphere, while the descending or south node is where the Moon enters the southern ecliptic hemisphere.

They are the reason for eclipse season, being the intersection necessary for the alignment of Sun, Earth and Moon.