This has quite a few meanings depending on use.
1. Header - word processing term. This a common area at the top of each page where text and logos can be placed. These can then made to appear on every page. The opposite of 'header' is 'footer' which is a common area at the bottom of the page.
2. Header - networking term. The 'header' in a data packet contains details such as destination address and source address. See 'Ethernet' in the glossary.
3. Header - a hardware term. This is a socket placed on a computer motherboard designed to accept power cables, disk cables and so on.
Challenge see if you can find out one extra fact on this topic that we haven't already told you
Click on this link: Header