When older equipment needs to be coupled with new, a situation often arises where the devices do not have the same sockets. These may be different compatible connectors, e.g. HDMI and DVI connectors, which can simply be addressed with a adaptor or a cable. But you may also experience types that are not compatible, and thus need an electronic converter, e.g. with built-in image-scaler.
Older signal types often suffer from being of a lower quality than what you are used to with newer signal sources. Therefore, some form of image enhancement is often needed, a so-called scaler, which is an image processor that sharpens the image and eliminates unnecessary noise.