A unit vector is a vector that has a length or magnitude equal to 1 unit. Unit vectors are used to indicate the direction of a vector in space. If we have a vector, we can obtain a unit vector with the same direction by dividing the vector by its length.
Unit vectors are very useful for indicating direction without regard to magnitude or length. In physics, for example, unit vectors are often used to indicate the direction of force, velocity, or acceleration.
In physics, when we want to decompose a vector into its components, unit vectors are very helpful. For instance, a force can be decomposed into components along the x, y, and z axes using unit vectors.