int[] is an integer array, so for instance, it's something like {1;2;3}. You know, the usual.
int[][] is an array of integer arrays. It's something like
{ {1;2;3}; {0;2;5}; {9;9;9} }
Notice how this is an array, because it starts with a { and ends with a }. The first element of the array is the array {1;2;3}. So it is an "array, where the elements are arrays".
Notice that this array of arrays has three elements (not 9).
Final comment: int[][] objects are how we represent matrices in Java. You read the first element {1;2;3} as the first row of a matrix, and the second element {0;2;5} as the second row of a matrix, and so on.
