hi Rober ...
don't let hang Your head...
read again Tom's post ... it is very clear described ...
look here:
so.
«anisotropic» simulates just a surface as it were heavily brushed in a specified direction. the brushing grinds a small landscape into the material, along the brush's path.
this landscape is very strong oriented and thus reflects light very specially. if light comes along the brush stripes, nothing special happens, but if the light comes from the sides, the topology is very strongly underlined. (highlight to shadow)
the examples above have ONE direction of the brush. let's say «up».
now. the option called «anisotropy» defines the «amount of brush work», the depth of the streaks. going from 0 to 100. and it can be texture mapped: black:0 to white:1
the angle now defines the direction, also via texture map. we've seen that the above examples show just ONE direction, so there was just a simple, linear input in the angle, which means direction: black.
black means: brushing UP.
now.
if this is textured, absolute white and absolute black show UP, all the other colors define the directions going from 0 degrees to 360 degrees, logically going from UP to left to down to right, and back up.
the image shown by JDHill shows exactly a texture which makes a material which is brushed in a circle, right around the center of the texture/material.
by using the angle option, with just one color (color picker), You choose the uverall texture brush direction.
best is to go ahead and really try on Your own. it's so easy!
best use the gradient tools in photoshop, as also JDHill's image was made in one minute.
have fun !