What's the racoon doing in my apple?

From Apple's documentation:

racoon speaks the IKE (ISAKMP/Oakley) key management protocol, to establish security associations with other hosts. The SPD (Security Policy Database) in the kernel usually triggers racoon. racoon usually sends all informational messages, warnings and error messages to syslogd(8) with the facility LOG_DAEMON and the priority LOG_INFO. Debugging messages are sent with the priority LOG_DEBUG. You should configure syslog.conf(5) appropriately to see these messages.

The documentation link of the main answer is now dead, but you can still run:

man racoon

and obtain an answer:

racoon is used to setup and maintain an IPSec tunnel or transport channel, between two devices, over which network traffic is conveyed securely. [...]