Loafers are lace less, low shoes with a separate sole and they sometimes sport a low heel. The upper vamp has a moccasin-like construction and sometimes loafers feature a piece of leather across the vamp, which is known as a saddle. This post is just a simple guide to choosing loafers, see below
The Wildsmith Loafer
The Aurland Loafer
The Penny Loafer
The Tassel Loafer
Wearing tassel loafers with a business suits would probably not considered to be a faux pas, but I still encourage you to wear it with casual suits and blazer / sport coat combination.
The Gucci Loafer
They are often combined with all sorts of outfits. Of course, using a black, polished box calf leather with leather lining and refining the shape make the loafer more formal than an off white, unlined Gucci summer loafer in suede but at the end of the day, it is still a loafer and not suited for tuxedos or white tie ensembles. Likewise, it is historically not appropriate to wear one with a classic three piece business suit because it is simply too casual.