Wiktionary
n. (context software of an application, operating system, etc. English) The combination of the visual design and behaviour of a user interface.
Wikipedia
In software design, look and feel is a term used in respect of a graphical user interface and comprises aspects of its design, including elements such as colors, shapes, layout, and typefaces (the "look"), as well as the behavior of dynamic elements such as buttons, boxes, and menus (the "feel"). The term can also refer to aspects of a non-graphical user interface (such as a command-line interface), as well as to aspects of an API – mostly to parts of an API that are not related to its functional properties. The term is used in reference to both software and websites.
Look and feel applies to other products. In documentation, for example, it refers to the graphical layout (document size, color, font, etc.) and the writing style. In the context of equipment, it refers to consistency in controls and displays across a product line.
Look and feel in operating system user interfaces serves two general purposes. First, it provides branding, helping to identify a set of products from one company. Second, it increases ease of use, since users will become familiar with how one product functions (looks, reads, etc.) and can translate their experience to other products with the same look and feel.
Usage examples of "look and feel".
If you had had a good many dealings in your time with personalities, you had a sort of feeling about them, just as an expert antique dealer knows instinctively the taste and look and feel of a forgery before getting down to expert tests and examinations.
He still remembered the cold wind blowing along the corridors and the look and feel of the place.
Human space aboard the Grand Luck meant this tiny stateroom, adjoining plumbing that made the Claw's spartan head look and feel like a spa, and one small bare chamber he could use for eating, exercise, and what recreation his own mind provided.
The mere look and feel of fleet communications, the charge of war electricity in the carbon-bluffed dispatches, stirred life in him.
Most people who shop for OSes (if they bother to shop at all) are comparing not the underlying functions but the superficial look and feel.