Bukkit

Each section will correspond to the key by the same name in the command description.

message

The message displayed is a list of lines that will be sent to the user. Each message can contain color codes (&0-F).

In addition, the variables <<recipient>>, <<triggerer>> and <<params>> will be parsed to the relevant values.

execute & executeAs

Any lines specified in execute will be treated as commands, and will be issued by the person you specify in executeAs. For players, commands must typically be prefixed with a forward slash (/), and for the console they must not be, but there are exceptions.

executeAs can be <<triggerer>>, <<everyone>> or <<console>>.
execute can contain any valid command, but will still be subject to permissions checks based on the the executor.

type

Type can be omitted for a "normal" command, "override" for a command that is trying to override any other functionality, or "cancel" for a command that you are trying to restrict to only certain users.

override - Any command with "override" will be cancelled and will only execute the information you provide in either an execute list or a message list (or both).
cancel - Any "cancel" command will retain its original functionality UNLESS the player who issues it does not have the appropriate permission node (ktrigger.command.commandname). If they do not have permission to use the command, it will be treated like an 'override' command.
normal - If 'type' is normal, or doesn't exist, the command is assumed to exist only as an alias and is treated as a normal command.