Question about variabl lists

This question will most likely have been answered a million times before, but how do you create a drop down variable list in the unity editor? Like the ones unity uses for making tags and input controls? I am trying to make a chess like game but to do so I need to connect the places in scripting, and for that I need one of those drop down lists. What is the scripting function to make a list like those stated above?

Use an array:

var something : Transform[]; // or whatever type