What is High-touch and low-touch trading?

High-touch trading hands an order to a person at the broker (a sales-trader or cash trader, One Quant Book 1, chapter 2), who works it with judgement, finds natural counterparties for blocks, and may commit the broker’s capital. Low-touch trading sends it to the broker’s electronic channels (algorithms, direct market access, smart routing), with the buy-side trader choosing and supervising.