What is a "hauberk"?

A hauberk is a type of armor that was popular in the medieval period. It was a long-sleeved shirt that was made of interlocking metal rings or mail. The hauberk provided protection to the upper body and was commonly worn by knights and soldiers during battle. The mail was typically made from iron or steel and could be quite heavy, so the hauberk was usually worn over a padded garment like a gambeson to reduce the weight and absorb the impact of blows. Despite its effectiveness, the hauberk gradually fell out of use as armor technology improved and firearms became more prevalent on the battlefield.