Static array types are denoted by constructions of the form
array[indexType1, ..., indexTypen] of baseType
where each indexType is an ordinal type whose range does not exceed 2GB. Since the indexTypes index the array, the number of elements an array can hold is limited by the product of the sizes of the indexTypes. In practice, indexTypes are usually integer subranges.
In the simplest case of a one-dimensional array, there is only a single indexType. For example,
var MyArray: array[1..100] of Char;
declares a variable called MyArray that holds an array of 100 character values. Given this declaration, MyArray[3] denotes the third character in MyArray. If you create a static array but don't assign values to all its elements, the unused elements are still allocated and contain random data; they are like uninitialized variables.
A multidimensional array is an array of arrays. For example,
type TMatrix = array[1..10] of array[1..50] of Real;
is equivalent to
type TMatrix = array[1..10, 1..50] of Real;
Whichever way TMatrix is declared, it represents an array of 500 real values. A variable MyMatrix of type TMatrix can be indexed like this: MyMatrix[2,45]; or like this: MyMatrix[2][45].