Part-time professors are usually treated the same as full-time faculty and are held to the same standards. The advantage to being a part-time professor is that they have are no other duties. When the class is over for the day, the adjunct professor may leave and go home or to another teaching assignment at a different school. Full-time professors must go to committee meetings, provide guidance to students, have office hours, and many other tasks.
Many adjuncts would object, arguing that they are most certainly not treated the same as their full-time colleagues (status, friendships, choice of classes, choice of schedules, etc.) and that their pay per workload ratio is significantly lower, mitigating the advantage of having "no other duties". Having no other duties and a fraction of the pay essentially means juggling two to four jobs at once. Your "other duties" are at other institutions.
He goes on,
Many professionals make a career teaching as a part-time professor since they can devote all of their time to teaching classes and earning money. Others use adjunct teaching as a way to supplement their regular income. A few retired people have told me that they teach as an adjunct to remain busy and to keep their minds alert. Many people teach because it brings them prestige to be called a college professor or that it enhances their image as an authority in their field. Yet others teach because they feel uplifted because they are making a difference in the lives of their students. Regardless of the reasons people become professors, it is a worthwhile endeavor.
But then again, many don't choose to be adjuncts. They simply can't find a full time professorship in this job market.
But if embrace this trend - that teaching higher ed is more and more a "side gig", something for retirees or people employed elsewhere and moonlighting in the academy for extra money or prestige, then we can contemplate taking this one step further and offering classes outside of the institution. One possible result is that the adjunct gets sucked into much of the adminitrative work that the university usually does: primarily finding students to fill the class and getting them to pay, but also organizing or providing materials and physical space for instruction.