Keypad library question

Projects Programming
1

I was working with the Arduino library for a keypad and its pretty simple other than one line that is a bit confusing.

#include "Keypad.h"
const byte ROWS = 4;  // set display to four rows
const byte COLS = 3;  // set display to three columns
char keys[ROWS][COLS] = {{'1','2','3'}, {'4','5','6'}, {'7','8','9'}, {'*','0','#'}};
byte rowPins[ROWS] = {5, 6, 7, 8};
byte colPins[COLS] = {2, 3, 4};
Keypad keypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );

In the above code can someone explain the line "char keys[ROWS][COLS] =......."

Is this an array, why does it have both [ROWS] and [COLS], i thought it could only have one set of []?
Please explain this line.

2

it is a 2 dimensional array or a matrix just like the keypad itself.