A heat-eye tube, also known as a cathode-ray tube (CRT), is a device that uses a vacuum and an electron gun to display images on a screen. However, there are some other terms used to describe this type of technology. For example, a CRT may also be called a picture tube, a tube display, or simply a tube. Additionally, it may be referred to by its method of operation, such as an analog display or a vacuum display. In recent years, CRTs have largely been replaced by newer display technologies such as LCD and LED screens, but they still have their niche uses in certain applications.