WOW! The biggest update yet! Big new features!
This update adds specifications for selectors, for example: "@r[gamemode=creative]"

There are 5 specifications that can be added to any selectors:

• gamemode
• tag
• limit
• distance
• level
  You can also add a "!" before a value to do the opposite. For example: "@a[tag=!"CoolTag"]"

For a list of what all of these do, and how to use them, refer to the spigot page documentation HERE.