"Orthogonality" is the term borrowed from geometry. If the two lines intersect into a right angle, they are orthogonal, such as the coordinate axes in the figure. With a vector term, these two straight lines do not depend on each other. Move along a straight line, you projected to the position of another straight line.
In the computing technique, the term is used to represent some kind of non-phase dependence or decoupling. If one of two or more things change, it does not affect other things, these things are orthogonal. In a well-designed system, the database code is orthogonal to the user interface: you can change the interface without affecting the database; replacing the database without changing the interface.
