Function as Data type i gotta question about it

i gotta question about function, anyway im using flash as3 for about 6 months, and im still kinda confuse in this things like getters and setters, and idk what you call that but here’s and example :

private function myBoolean():boolean
{
//codes here //
{

idk how to use it, and what it differs from getters and setters,
hope somebody can answer this things. anyway thanks in advance for your help guys…

-raphaelle
cheers.