The proper identity of sectional factory-built homes routinely stumps North Carolina Listing Agents who often mistakenly label these homes.

Factory-built homes may be "modular" or "manufactured."
The existence of a steel I-beam frame and wheels is not a distinguishing factor.
The method of installation, via crane or roller system, is not an indicator. The amount of finish work required on-site is an irrelevant factor in distinguishing which it is.
The Building Code to which it is built to conform is the identifying factor for sectional housing.

"Manufactured" homes replaced the "trailers" or "mobile homes" of the 1950's to the early 1970's.  The "Manufactured" name is very specific.   It was coined when HUD assumed code and quality regulation on a national basis in 1976.  They may also be identified as "HUD Code Homes."

Manufactured homes usually have a steel frame, but can be constructed with a unified floor/frame system that eliminates the traditional, visible frame.
They can be single or multiple sectional. Some manufacturers have dabbled with two-story or 1 1/2 story units.
They can be set with a crane onto a crawl space or basement, sold with a piece of land, in a "land-home" package, with a deed. But there will still be a title for the manufactured unit.
Or they can be rolled onto a pier foundation typically associated with "trailers."

HUD Code Homes may also be sold as chattel, and installed in parks on rented sites.

The easiest way to identify one is to locate the red "HUD Tag." It is a metal plate, approximately 1.5 inches high x 4 inches wide.  The tag has an ID number similar to a VIN stamped into it. The HUD tag will be attached to the siding, on the rear end of a single section unit, and on the trailing end of the side of a multi-sectional unit, approximately 12 inches up and 12 inches from the corner of the unit. You can see the tag from 200 feet away if you can see the location on the home.
Mobile and manufactured homes convey via transfer of a vehicle title.  It is important that the Seller has the title to the home, as well as the deed to the land.

Homes can be also be built to local codes in a factory. That qualifies them as some sort of "modular."
"On-frame modulars" satisfy local codes for the destination to be shipped to.  Typically there is a little more, and larger dimensional, framing lumber, updated and upgraded electrical and plumbing systems, plus any other niceties to satisfy the foibles of local officialdom.
On-frame modulars were created to sell manufactured housing to people in areas where restrictive zoning codes limited the installation of manufactured homes.
Experienced structural engineers, and all of these companies employ several of them, can design an on-frame home that looks like a trailer but meets local codes for construction.

"True" modular homes, also built to local codes, come on a carrier frame, are removed from that frame and set on a foundation that meets local code standards. They may have as many sections, in whatever configuration, as the designers can dream up.
They appear very similar to stick-built homes, but also can have differences that may not be readily observable to the casual observer.

After manufactured homes and modulars, factory-system building is a wide-open discussion.
Panelized homes may have walls framed and sheathed. This method is popular with large builders who buy or build wall sections that are trucked to the site and assembled by the framing crew.  This saves time in on-site work, and helps get a home "dried-in" more quickly.

Some companies even ship panels with windows installed.
Pre-cut homes may be just that, pre-cut framing members, resulting in a kit of studs, joists, rafters, etc, to assemble on-site. And homes are built with a combination of methods, with transitional or complex areas framed on-site, garages, decks, and porches added on-site, etc.

It is important to gain ability to identify the type of home being listed, as inviting other agents and their Buyers to visit a "Ranch Home" that is actually a double-wide HUD Code dwelling reflects poorly on the Listing Agent's professionalism.