First of all, you have to know theese two words: Actions and Requirements.

Actions
These are things that executed when all requirements is met.

Command Action | Executes a command. | type: COMMAND
Required entry: ' command' | String

DropAction | Drops an item at entity's location. | type: DROP
Required entry: 'item' | XItemStack

GiveAction | Gives item to killer. | type: GIVE
Required entry: 'item' | XItemStack

Requirements
These are required scenarios to run actions.

ChanceRequirement | Chance. | type: CHANCE
Supports any double between 0.0 and 100.0
Required entry: 'chance' | Double

TypeRequirement | Entity's type should equal to this. | type: TYPE
Click here for list of all entity types.
Required entry: 'entityType' | EntityType

NameRequirement | Entity's name should equal to this. | type: NAME
Supports any double between 0.0 and 100.0
Required entry: 'name' | String


Examples

1. It will check is entity's type equal to ZOMBIE.
2. Then it will check is entity's name to "hombie".

If above requirements are met, below actions will be executed.

1. It will drop a STICK
2. It will give the special diamond to killer.

Note: You can use "§" instead of "&" for colorizing.