Before we discuss about orthogonal vectors we need to know about what exactly orthogonal mean. Orthogonality is derived from the Greek word orthogonias (orthos means straight and gonia referred as "angle" ) which gives a meaning of "straight angle".
It is used in many fields such as Mathematics, physics, chemistry, etc. It has a wide application in the area of applied Mathematics. Particularly linear algebra, Euclidean geometry and spherical trigonometry. Orthogonality which takes the meaning of 'Perpendicular'. When two vectors that perpendicular to each other are called "orthogonal vectors".