The projection angle defines the method employed to generate projected views.
First Angle Projection
When you use first angle projection, projected views placed to the right of a base view depict the appearance when viewing it from the left. Projected views placed below the base view depict the appearance from above. The ISO drafting standard specifies that drawings use the first angle projection angle.
Third Angle Projection
When you use third angle projection, projected views placed to the right of a base view depict the appearance when viewing it from the right. Projected views placed below the base view depict the appearance from below. The ANSI drafting standard specifies that drawings use the third angle projection angle.