Description
The simplest use of this function is to define a matrix by giving a doubly nested list of ring elements. One may also explicitly provide the ring, or give a matrix as a doublynested list of matrices.
i1 : matrix{{1,2,3},{4,5,6}}
o1 =  1 2 3 
 4 5 6 
2 3
o1 : Matrix ZZ < ZZ

i2 : R = QQ[x,y,z];

i3 : matrix{{x,0,2},{1,2,y}}
o3 =  x 0 2 
 1 2 y 
2 3
o3 : Matrix R < R

The
map function provides other methods to define a matrix.