Also, "line level" is a commonly agreed on electrical value (value range?) that comes out of most equipment and goes into a receiver, preamp, whatever. Line level is a standard that lets you use company-x's preamp with compny-y's amp (without blowing it up!). The exception to line level is a phono signal. This uses a different standard and is why you can't plug a CD player into the phono jacks of your receiver.
