What’s the difference between a Fast wide pipe and a Narrow pipe construction?
Of an iterated hash function $$H(m_0 \mathbin\Vert m_1 \mathbin\Vert \cdots \mathbin\Vert m_{n-1}) = g(f(\cdots f(f(\mathit{IV}, m_0), m_1)\cdots, m_{n-1})),$$ for functions $f\colon \{0,1\}^s \times \{0,1\}^k \to \{0,1\}^s$ and $g\colon \{0,1\}^s \to \{0,1\}^h$, narrow pipe, as introduced by Stefan Lucks, just means that the intermediate state is no larger, or not much larger, than the final output: $s = h$.  Wide pipe means $s \gg h$.

In SHA-256, the intermediate state has $s = 256$ bits just like the output; thus SHA-256 is a narrow-pipe iterated hash function.  In SHA-512/256, the intermediate state has $s = 512$ bits and the output has $h = 256$ bits; thus SHA-512/256 is a wide-pipe iterated hash function.  In SHA3-256, the intermediate state has $s = 1600$ bits while the output has $h = 256$ bits; thus SHA3-256 is also wide-pipe.

In principle, SHAKE256-1600 would be considered narrow-pipe too, but such distinctions are not really used much these days; they don't illuminate relevant security properties very well.  The attacks that Lucks hoped to thwart with wide-pipe constructions are usually addressed in other ways instead, and we aim for security targets rather than pipeyness.