Though not commonly used in English, in many European languages, the word objective is used as a noun describing the "lens" of a camera or a film/slide projector.
I put the word lens in quotation marks because, strictly speaking, few if any modern cameras use just a single lens. They typically use a lens assembly, i.e., an objective.
The objective (lens assembly) usually consists of a metal tube in which several lenses are assembled.
The objectives designed for the use in view cameras and other bellows cameras generally use a simpler design in which the lenses are mounted in a fixed distance from each other. That is because focusing is achieved by changing the distance of the objective from the film, i.e., by collapsing or extending the bellows.
In some of the non-bellows cameras, the objective, too, contains lenses fixed. These are the cheap cameras with fixed focus, which make more or less everything from a certain distance to infinity (relatively) sharp.
However, most non-bellows cameras use objectives with movable lenses. Focusing is achieved by changing the distance of the lenses inside the objective. This can be done manually, by the photographer, or automatically in point and shoot cameras. The automatic focus generally focuses on whatever object in the center of the image is the closest to the camera. This is really not a good idea because it wastes part of the depth of field on just the empty space in front of the closest object. Just another example of a supposed ease of use sacrificing quality.
Most modern objectives also have a built-in shutter, which, again, is either controlled manually or electronically (in the point and shoot cameras).
Various objectives contain other built-in features, which is why the common English custom of calling an objective a lens is rather inexact, though a fact of life.
A bellows camera is somewhat harder to use. However, one of its advantages is that since focusing is done by the bellows, interchangeable lenses (I mean objectives) do not need to contain the extra feature of movable lenses, hence they should be cheaper (at least in theory, though in practice they may not be because fewer of them are made). The bellows cameras have many other advantages as well, but those are oustside the scope of this write-up.
Incidentally, the lens assembly got its name "objective" because it creates the image of an object.