Arrays and Classes javascript

Here is a class Card and a 2d array aGrid.

The 2d array aGrid is set to aGrid = new Card[4,4]; it looks like I am making it an instance of the Card class and an array at the same time. How does this work??

I thought a variable could only be set to one type of thing ---> an object instance or an array but not both.

Here is the code:

 class Card extends System.Object {
     var isFace:boolean = false;
     var isMatched:boolean = false;
 }

 var aGrid:Card[,];//2d array to keep track of the shuffled, dealt cards

 var aGrid = new Card[4,4];