Any sales process where each customer needs a small amount of personal attention. For example, a McDonald's drive-thru customer is a very low-touch operation. The cashier only needs to guide the customer through a streamlined process, with very little individual variation.
Contrast this with high-touch sales, where (at the extreme end) a 5 year lead time and several corporate jets may be involved, or with Zero-Touch sales, where software is used to take the customer's money while the business employees are asleep. A humble first product can easily achieve zero touch sales, though there is a catch: see concierge onboarding.
My book "Choose Your First Product" is available now.
It gives you 4 easy steps to find and validate a humble product idea.