Here is a 26 second YouTube clip that actually explains it all without saying a word. I get it now.

Basically, the Galactic plane runs through our sky. Because the galaxy is really big, and we're not (thank you Warners), the Galactic plane extends far above and below the Solar plane, but does not actually cross it, in a physical sense. At two points along the ecliptic (Solar plane), the Galactic plane seems to cross it, as seen from Earth. It's a perspective thing. The Galactic plane just extends out so far that it's long enough to look like it dips below the ecliptic. On the Winter Solstice, from 1994, to 2012, the disk of the Sun will cover that spot where the Galactic plane seems to cross the ecliptic.

Maybe someone else can say it better, but basically, it's an event about like an airplane blocking out the light from Venus from where you're standing. And just about as significant.

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A Nerd can figure out how long it will take the original Enterprise traveling at warp 6.5 to travel from Regulus to Antares.
A Geek will think he can use that to pick up a girl in a bar.
A Dork knows he can't pick up the girl with it, but will hang around for hours anyway, just in case she asks.
She might. You never know.