An isometric drawing shows what a form looks like but it may not provide enough information to make the form. There may be some details in the hidden surface that we cannot see.
To overcome this problem, designers use drawing called orthographic projection in which full detail of a form can be shown.
An orthographic projection shows the form viewed from different positions. Consider the example of this toy train.
The view from the front is called the front elevation.
The view from the side is called the side/end elevation. This is normally viewed from the left-hand side.
The view from the top is called the plan. It is seen from above the front elevation.
In a first angle orthographic projection, the plan appears below the front elevation.
The end elevation is drawn to the right of the front elevation.