This equation computes the sum of two orthogonal vectors.

This is one of the simplest ways to show vector addition since one vector is purely in the y-direction and the other vector is in the x-direction. See Vector addition by components to see vector addition of two vectors show have both x and y components.

Note that to simplify the graphical example and the explanation of vector addition, we show vector `vecA` begins at the origin of the Cartesian axes and so vector `vecA` points in they-direction.   Nevertheless, we know that vectors are defined by their length and direction and can thus occur anywhere on the X/Y plane and still be the same vectors.  That principle of vectors is also why you can add `vecb` to `veca` by placing the tail of `vecb` at the head of `veca` and get the same resultant vector as when you add `veca` to `vecb` by placing the tail of `veca` at the head of `vecb`.

Notes

A vector is a mathematical concept of an object that has direction and length.  A line alone is not a vector but a line with orientation spanning the distance between two points in space is a vector.

The graphic shows that `vecc` = `veca` + `vecb` = `vecb` + `vecz`