what are bootable membership cards

http://member.fsf.org/benefits.html Bootable Membership Card You will receive a personalized, bootable, business-card-sized GNU/Linux distribution as your membership card. This GNU/Linux distribution is based on LNX-BBC. New cards will be sent to renewing members every year if and only if there is a new major release of LNX-BBC. Note: The first version of the membership cards will be shipped on Tuesday 25 February 2003.