Without getting too mathy - matrices let you express useful transformations (eg. translation, rotation, scale) and multiplying two matrices combines those two t

Without getting too mathy - matrices let you express useful transformations (eg. translation, rotation, scale) and multiplying two matrices combines those two translations - so you can have matrix tansform = rotationA * translation * rotationB and now multiplying a vector (~ a 3d point) by that transform matrix is the same as doing each individual transformation (in the reverse order they appear in matrix multiplication) on a point to get the point after transform