What does L1 L2 and N mean in electrical terms?

L1 and L2 stand for "Line 1 and Line 2". These are the two incoming hot legs of a single phase, 220V electrical supply as is typical for residences.

The N stands for the neutral or grounded conductor. This is the white wire in a residential system.

Since L in electricity stands for inductance, L1 and L2 could also possibly be inductor 1 and inductor 2. And the N in electricity means Number of Turns (of the copper wire into a coil). Therefore, it could be about residential wiring or inductors.