What is the definition of SamplerState hlsl type?

I tried a file search into the *.ush and *.usf files and could not find the actual definition of the SamplerState hlsl data type.
Is this type specific to Unreal Engine HLSL?
Is it exactly the same as “sampler” a standard HLSL data type?
Can I use this in a custom blue print HLSL node? Like this?
SamplerState MySamplerState;
MySamplerState.variableName1 = something.
MySamplerState.variableName2 = something else…
etc…?