Consider a vector #vecv#, for example, in space:
If you want to describe it to, say, a friend you can say that has a "modulus" (=length) and direction (you may use, for example, North, South, East, west...etc.).
There is also another way to describe this vector.
You must take your vector into a reference frame to have some numbers related to it and then you take the coordinates of the tip of the arrow...your COMPONENTS !
You can now write your vector as: #vecv=(a,b)#
For Example: #vecv=(6,4)#
In 3 dimensions you simply add a third component on the #z# axis.
For example: #vecw=(3,5,4)#