Key logging is a Mac only feature (i.e. it doesn't work on iOS due to iOS development constraints) that allows you to track the keystrokes of anyone in possession of your laptop whilst tracking is active. Sometimes the key log reports can look funny as they contain all sorts of strange symbols for various keys. For example the Command key will show up in your key log as "cmd" with angle brackets either side.
Key logging requires two packets of tracking data to be returned before it can display anything. Consequently, you'll need to have tracking active for approximately 20 minutes before key logging will return anything. You can give this a go by setting your Mac to 'Stolen' and waiting for two packets of data to arrive.