What causes fluid friction?

Hello world,

I have a question on what causes the friction of a fluid like water or air
upon a surface while it is moving?

I understand basic some things like fluid/air pressure upon the object, the
fluid's viscosity and fluid 'layers' [By that I mean the slowing physical
'state' of movement of each layer of particles the closer you get to the
object.] I think the best example is a black hole...the closer you get to it
the slower time goes til it basically stops.
If I understand it correctly, if my interpretation is right... is it kind of
related to the theory of relativety? ( correct me if I am wrong in any
place). :-)

So i guess perhapse knowing that stuff...is friction cause by the attraction
of the fluid to the solid at an atomic level, or is it air pressure, or
attraction of molecules of the fluid type to the solid type or the transfer
of kinetic energy from one place to another...?

Regards

Robert

I know this is a space forum but there aren't many science forums...