A sitelink is an extra link shown under an ad, pointing somewhere other than where the ad itself points: the donate page, the volunteer form, the particular programme. Callouts add short lines that are not links, and structured snippets add a labelled list. Google calls these assets now; most people still say extensions.
They do two things at once. They take up more of the results page, which makes the ad harder to skip, and they offer a reader more than one reason to click — including the reason they actually came for, which is often not the one the ad is about.
Why they are not optional here
On a grant account the thing they add is click-through rate, which is the thing the programme measures. They are also required: Google's account management policy asks every Ad Grants account for at least two unique sitelink assets, and names account structure among the things an account can be deactivated for.
- At least two, which is the policy minimum; two to four per campaign is the shape that usually earns its keep, each pointing at a page that answers something different.
- Callouts for what is true and short: “No appointment needed”, “Open Saturdays”, “Serving the whole county”.
- A structured snippet listing the actual programmes, which is also the cheapest honest way to say what the organisation does.
Questions people ask
Do they always show?
No. Google decides per auction, and a higher Ad Rank makes showing them more likely — which is part of why position and click-through rate reinforce each other in both directions.
Campaign level or ad group level?
Campaign is the sensible default. Drop to ad group level only where the links would genuinely differ, or you will be maintaining four copies of the same four links.
Can the agent propose them?
Yes — sitelinks, callouts and structured snippets are all things it can write into a proposal. A specialist applies it, as with any other change.