steeping is just the act of soaking an item in a liquid in order to gradually remove components from it. In the case of your wort, you are steeping the grains to gradually add fresh malt character that might be missing from the extract. The crushed grains add sugars to the water as they soak.
I think John Palmer in How to Brew equates it to steeping tea bags in water. You want to steep it just long enough to get the right flavor out of the grains...but not too long that it develops a disagreeable flavor.
Just avoid boiling. Play with the burner setting for a little bit until you get the water standing at 150-160*...then add grains
Primary: Mexican Cerveza
Primary: Chimay Blue clone
Bottled Fox Hound Irish Red
Bottled: Blue Moon clone from AHB
Bottled: Unnamed Stout
Next up: Mexican Cerveza