What is a Headshell and what does it do ?

Trying learn a few things here .
I see removable headshells and people talking about changing cartridges with them . Why ?

Thank you

saki7002-17-2015 6:41pm

ebm Details Discussions Posts This discussion Message User 9,311 posts 02-18-2015 at 12:59am Copy Comment URL Report Comment Edit Delete Wow this question is to tough.