Gateway page
A gateway page, or doorway page, is a thin page made only to rank for a search and pass visitors on somewhere else. Google treats it as spam.
A gateway page, more often called a doorway page, is a page made to rank for one search and then send the visitor somewhere else. It has little of its own to offer. Its job is to catch the click and pass it on, sometimes with an automatic redirect, sometimes with a big button to the real page.
Google lists this under "doorway abuse" in its spam policies, and pages that break those policies can rank lower or drop out of Google's results.
What it looks like
The classic version is a set of near-identical pages, one per town. For example, a coffee delivery company publishes "Coffee delivery in Leeds," "Coffee delivery in York," "Coffee delivery in Hull" and forty more. Each page has the same three paragraphs with the town's name swapped in, and each one links to the same order page. None of them says anything about Leeds, York or Hull that a person could use.
Google's examples include several domains with small variations that all funnel to one site, and pages that are closer to search results than to a page someone would choose to browse.
When a page per place is fine
Pages per location aren't spam in themselves. A page for each of your shops, with its own address, opening hours, staff, parking and photos, is useful to the person who lands on it. The test is whether the page would still be worth reading if search engines didn't exist.
Gateway pages and AI answers
An AI platform reads a page looking for something it can use in its answer. A doorway page has almost nothing to take: no facts about the place, no prices, no reason to choose you. So even when one gets read, it gives the answer little to repeat. A single strong page that lists the towns you deliver to, with real delivery times and costs, gives the platform more.