Nonsquare
3 by 2 matrix, which means projecting 2 dimension to 3 dimension.
2 by 3 matrix, which means input is 2 dimension and output is 3 dimension.
1 by 2 matrix, input is a 2-D vector and output is a number. (related to dot product)
Reference
https://www.3blue1brown.com/topics/linear-algebra