Offset path Tool versus Object menu and Effect menu

Question

After a strugle with the ofset path tool I find the solution...
Offset Path in the effects menu acts totally different thean ofset Path in the Object menu WHY?
What happened;
Offset path in the effects menu gives you a centerline with offset path which isn't modifiable..
for in stance in my kind of work i want to create a paralell road on one side of the main road.
the offset path in object menu gives me the right result, an offseth path which I can cut and modify.
It should have been easier if the different behavior was in an offset Path tool menu...

Answer 1

Offset Path in the effects menu acts totally different thean ofset Path in the Object menu WHY?
Because the command in the Object menu is a straightforward path-modifying command. You select something, apply the command, and the result is a new path.
Everything in the Effect menu is, in Illustrator parlance, rendered as a "live" effect. That is, the program creates the modified version sort of "behind the scenes." That lets you continue to modify the original path, and the Effects that you have applied automatically re-apply on-the-fly. So instead of Offset Path giving you an new path that you can no longer manipulate as if it is one stroked path, Effect>Path>Offset Path lets you continue to work with the single path without having to start over every time you want to change it.
An Effect can be "nailed down" to "literal" new objects by using an Expand command.
Offset path in the effects menu gives you a centerline with offset path which isn't modifiable..
The offset path is "modifiable" in that you can change the attributes of the Effect any time you want. The offset path is also "modifiable" in that you can re-shape the path to which the effect is applied, and the offset path updates automatically. That's a good thing.
for in stance in my kind of work i want to create a paralell road on one side of the main road.
So when you're done manipulating the orginal path, and you now want to "nail down" the offset path as a separate path that you can modify, select Object>Expand Appearance.
the offset path in object menu gives me the right result, an offseth path which I can cut and modify.
Yes. But it's frankly rather lame. That is, if you now need to bend the whole road in another direction, or alter one of its curves, how are you going to do that for both sides of the road at the same time? With Offset Path applied as a live effect, you can. With Offset Path already Expanded, or applied as the older...uh...dead...command, you can't.
So it's your choice. The interface is needlessly awkward and confused, because when Adobe adds new features it seldom does a good job of integrating them with the existing features. So you end upon with both the older and newer features which essentially do the same thing. That's the nature of Illustrator--it becomes increasingly inelegant, cluttered, and confused over time.
One example to the contrary: CS4 finally did away with the separate Filters menu, which was just the old, "literal" versions of most things in the later "live" Effects menu (all of which can be turned into "literal" versions by an Expand command). It was hideously confusing for newcomers to Illustrator to see the same things listed in two menus, one labeled "Filters" and the other labeled "Effects." On the face of it, what's the difference between a "filter" and an "effect" in most people's minds?
One case-in-point example: The Effects menu has a list of Pathfinder Effects that mirror the names of the command that reside in the Pathfinder Panel. But they do different things; they are meant to be applied to different kinds of objects.
Such is the nature of Illustrator. It's a hodge-podge, grab-bag collection of scattered features which are often redundant and often poorly integrated with each other.
It should have been easier if the different behavior was in an offset Path tool menu...NO! The last thing this program needs is more off-the-cuff, willy-nilly, ad-hoc palettes. It needs a thorough interface overhaul, with a dedicated and careful eye toward concise elegance and organizational efficiency. That would be a very ambitious undertaking because the program has been allowed to become such a rat's nest of disarray. 
JET