I'm new to this, too, but I've made a few single malt/single hop brews (even really light on hops) just so I can taste the differences. And I'm still an extract brewer.
The light malt is 1) light in color, and alittle sweeter/cleaner in flavor. There are no caramel notes.
On the flipside, the dark extract is much richer in color, and has a VERY caramelized flavor.
The scale moves between the two incrementally, but the caramel (burnt) notes are more prominent the darker the malt. Likewise, the color is, too. The color is a byproduct of the toasting process used on the grains that imbue this flavor and color, and sometimes, end up becoming extract.