One index buffer with multiple vertex buffers?

One index buffer with multiple vertex buffers?

I noticed that there's IASetVertexBuffers() to set multiple vertex buffers
at once but there's only IASetIndexBuffer() to set one index buffer. So I
assume that I can simultaneously only have one index buffer set but I can
have multiple vertex buffers set at the same time.
Is that correct?
How do I use index buffer with multiple vertex buffers? I.e. what indices
do I provide to use more than one vertex buffer and how do I know what
buffer conrete indices refer to?
Or is this used only in the case when instead of interleaved vertex data:
(Pos, Normal, Pos, Normal, Pos, Normal) I provide the data in multiple
buffers: (Pos, Pos, Pos) (Normal, Normal, Normal) and conrete indices
refer to the same vertices in each buffer?