What do "Header" or "Error" mean in the "Main Tests" column in the VClips list of clips?

What do "Header" or "Error" mean in the "Main Tests" column in the VClips list of clips?

The "main tests" column essentially describes what portion of the decoder that particular clip focuses on stressing. For example the error Vclips stress the decoder by introducing errors into the stream to see how well the decoder under test handles them. The header clips stress a wide range of header information and values to see if the decoder can handle all the different header settings available in the standard. This is why there is such a large range of resolutions in the Header test clips, because the specified resolution is one of the header components these clips are designed to stress.