Video Adapters change the physical connector but do not change the video signal. These may be passive adapters, when they are just changing the shape of the connector; or may be active; when they boost the signal. Composite RCA to BNC is a good example of a Video Adapter.
Video Converters translate the video signal from one format to another; and may also change the connector. Composite to HDMI is a good example of a Video Converter
Formats which are electrically and protocol compatible:
If a video signal is electrically and protocol compatible, then only changing the connector type is required.
Composite <> BNC : are electrically compatible and only requires an adapter.
VGA <> DVI-I : Analog and are electrically compatible only requiring an adapter;
DVI <> HDMI : HDMI is backwards compatible with DVI televisions. DVI computer monitors support several DVI standards and may or may not be compatible.
DispalyPort <> HDMI: Displayport is backwards compatible with HDMI and DVI.
Formats which require electrical and protocol translation:
Formats that require electrical translation require a capture step, a translation step, and a re-encoding step. In glitch art, a problem arises at this step that sync information may have been glitched and the converter cannot make sense of the input signal.
Composite <> HDMI requires a converter