The line spectrum is also known as the emission light spectrum.
The ELS shows what colors of light are released when an element(or a specific compoud) is burned or electricity is sent through the gaseous form.
The ELS can be used to identify elements because each element has a different ELS. Elements like Tungsten produce a white light when burned, so their ELS has many line close together. This is why tungsten was used for lightbulbs.