DSLR models typically offer interchangeable lenses, large image sensors, full manual controls, external flash units, and through-the-lens (TTL) viewfinders. They're large models and they closely resemble the 35mm film cameras that were popular several years ago, with handgrips and large lens housings.
A digital camera model that looks like an SLR, but that doesn't offer a TTL viewfinder or interchangeable lenses, is called an DSLR-style camera or a fixed lens camera. Such cameras are aimed more at intermediate photographers and can serve as a bridge between a point and shoot camera and a true DSLR.
A new classification for interchangeable lens cameras, called DIL or EVIL, makes use of a mirrorless design. Such cameras technically are not DSLR cameras.