Security keys
A security key or token enables other systems to access Moodle securely. A security key may be used for secure RSS feeds or web services.
A user can obtain a security key via Settings > My profile settings > Security keys then enter the key in an external application accessing Moodle.
At any time, a user can reset their key by clicking the reset link. A new different key is automatically generate which will then need to be entered in the external application.
Note: the security keys page can not generate web service keys/tokens for admins. Admins can create a token manually from the administration block: Administration > Plugins > Web services > Manage tokens.
Secure RSS feeds
Secure RSS feeds is a feature allowing users to have a RSS feed with a 'secret URL'. The idea is that the URL is not guessable and ensures that only the person whose URL it is can access the feed. (The reason to do this rather than ask for a username and password is because many RSS readers such as Google reader do not support using a username and password to access RSS feeds.)