An on-site survey is a special type of a questionnaire survey. For an on-site survey, an online questionnaire will be created. Afterwards, participants are recruited directly on the website that is being tested. This can be worthwhile, for example, when users’ experience with the website is being investigated. Recruiting participants directly on the website guarantees, that all participants know the website and have used it before.
Find a detailed description of the method here: On-Site Survey