What is the difference between a BELT line and a TRUNK line?

I was flipping through some old Model Train magazines, and I came across an article about how this guy made a layout where there was an interchange between a City Belt Line and a Trunk Line.

I get that a Belt line connects the different railroads in the city to each other (Like the Belt Railway of Chicago, or the Indiana Harbor Belt) but I dont know what a TRUNK line really is (like the Grand Trunk Western). Can someone explain to me what one is? I would rather appreciate it. =]

What is the difference between a BELT line and a TRUNK line?coolest myspace

Both are another name for a "short line", which, as its name implies, has limited trackage, equipment and employee roster, and often times connections between larger railroads or in a field of special service.

These days, many have been created by common carriers on the branch lines they used to operate, under a new railroad name, usually non-union, which is the perfect vehicle for union busting.

What is the difference between a BELT line and a TRUNK line?myspace comments myspace.com

Just sounds like the names they just used to identify which train ran which route.