An AI mention is the moment your name appears in an AI answer. That can be in the text (“At De Korenaar bakery in Zwolle you can...”), in a list of providers or as a link to your website. If the answer links to your page as support, it is a citation.
A mention without a link can still have value: the reader learns your name.
Why is it hard to measure?
The same answer rarely comes back in exactly the same form. The outcome depends on the question, the platform, the moment and the settings. OpenAI writes in its help page on searching with ChatGPT, for example, that ChatGPT can use a general location and saved memories when it rewrites a search. Two people asking the same question can get different answers.
How do you check it?
Use a fixed set of customer questions, always in the same environment and at an agreed time of measurement. For each answer, record the question, platform, date, settings, whether you are named, with or without a link, and which other providers appear. Outseen checks AI answers this way, by hand.
Common mistake
Treating a single screenshot as proof that you are “in ChatGPT”. One answer says little about the next one. Look at repeated measurements with the same questions.
More in How do you measure your visibility in AI answers? and under share of voice.