Some articles on headers, header:

Simple Common Gateway Interface - Specification - Request Format
... A request consists of a number of headers and a body ... The format of the headers is headers = header* header = name NUL value NUL name = notnull+ value = notnull* notnull =
Common Aftermarket Exhaust Parts - Headers
... Switching from an exhaust manifold to exhaust headers (also known as extractors in Australia) will optimize the exhaust gas flow speed and in turn increase the high-end power of the engine ... With equal length headers, as each exhaust valve in the head of the engine is opened and exhaust gas is forced out, it passes down one of the header pipes and through to the down pipe, where the ... The length of exhaust headers can be tuned to perform best at specific RPM ranges ...