Netzspannung means "mains voltage". Normally in Germany this would be 400 volt three phase (used to be 380 volts, see
this document for details.) . This means five conductors: E (earth), N (neutral), and L1, L2, L3 (lines). Voltage between any two of the lines L is 400V, voltage between any line L and N is 230V.
Lichtspannung means "lighting voltage". Normally in Germany you have three phase power coming to a house, and the electrical sockets in the house are connected to N and one of the three lines L. So this is the 230V Lichtspannung.
Bottom line: Netzspannung means "400 volt 3-phase" and Lichtspannung means "230 volt single phase" (usually derived from the 3-phase as described above). This is sometimes written as 230V~1/400V~3.