What does it mean when one wire goes into load, and one goes into line
Line is the side of the device where the wires from the panel (or other equipment feeding the device) are connected.  Load is where any devices that are to be protected by the GFCI device are connected.  

Most "newer" GFCI devices will not reset if they are not connected probably.  

GFCI devices use a current transformer (CT), to detect any current differences between the "hot" and "neutral" conductors. The LINE terminals are on one side of the CT, while the LOAD terminals (and the receptacles on the device) are on the other.