Answer 1

An array is a list of elements of the same type. They are registered in a continuous list, or you can say that they have a single dimension, the x axes. When you declare with two "for" functions a two dimensional array, you create a matrix with columns and rows, like the first array, but in addition with values from up to down.
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You can put it on the x and also y axes. With tridimensional array will be the same, but there will be the z axes in addition, like making a matrix and arranging the elements in a 3D form. From this dimension and up it will be harder to manage the elements, so I recommend to use only 2 dimensions, the third only simetimes.