Sometimes this is regarded as industrial design. But generally speaking design technology is about the tools and techniques for the creation of practical designs of technological solutions to problems. Design can be thought of as a practical application of art. Art does not have to have a function but design does, hence the expression "designed for..."
Design technology is a very diverse field that can range a spectrum from mostly pure engineering to mostly aesthetic characteristics.
Human design technology
Furniture for example is a design technology to create a means to allow a person to sit. This could be the design of a chair. But the design of a chair relies on what the problems are with sitting, for example the angle of supports, whether there are different supports or how it fits with other components.
Industrial design technology
Considers the form of a technological device to suit a particular need or want. If the technological device needs to be held in the hand for example (ergonomics). Industrial design is usually also considered on a large scale production of particular designs.
Fashion clothing design technology
These are tools and techniques for the creation of clothing fashions to cover the human body. Sometimes this has practical requirements such as protective or supportive design elements.
Musical instrument design
These are the tools and techniques for creation of musical instruments and use similar techniques to other designs. Often it involves techniques of joining or welding similar to carpentry.
House, garden, landscape design
These are related to the tools and techniques for organising items around a house, garden or larger landscape, usually for human habitation ( or in the case of zoo, for animal habitation) or use in someway.
Architecture would be specialised kind of engineering design
Examples of technology designs: