The Pitot Tube is located away from the aircraft skin so as to remove it from the aircrafts "boundary layer".
The boundary layer is the layer of air between the surface and the free stream velocity in which local retardation takes place. Like the main airflow, the boundary layer flow can be either laminar or turbulent in nature.
In order for the Pitot tube to then face the oncoming airflow it is angled (roughly 90degrees)
I think thats the answer you are looking for.