What is an Associative Array? [on hold]

QUESTION:

What is an Associative Array?

ELABORATING ON QUESTION:

The syntax I see when searching an Associative Array is as follows:

$myArray = array(
    "car" => "truck", 
    "price" => 50000
);

and I would love to know what the structure of the array does, the purpose of an Associative Array, and some examples so that I can have a complete understanding for future use.