I am reporting on a science project that involves an EPG monitor and have to discuss what Lin/Lout refers to. I honestly just have no idea what it means when referring to electric circuits. Any help?

 

line in, line out. references a low level usually 600 ohm audio cable connection between equipment.

 

Line level signals are usually in the range of 1.1 volt peak. Just know you are dealing with a signal that is large enough to be well defined compared to local noise, and isn't much higher than a volt or two.

Theoretically, it is .775 volts RMS driving a 600 ohm load, for a result of one milliwatt.
In practice, it varies.