AB can be written as the sum of the outer products of column i of A with row i of B. The keyword here is the outer products. xᵀy is different from xyᵀ. This is another perspective of describing the same thing. Here is how it may be used from this perspective.

https://www.quora.com/What-is-an-intuitive-understanding-of-the-outer-product-of-two-vectors