Individual websites are organised according to a certain algorithm and displayed in the list of results in accordance with their ranking. It is not fully transparent, which criteria are applied to the search results. It is, however, known that commercial interest plays a role.
The ranking in general search engines provides little insight into the actual relevance of the results.

General search engines do not apply any systematic quality criteria that comply with academic standards, as summarised in the CRAAP test in chapter 1 of our course. The scope of the results is rather wide: from sources with no academic substance to those with high academic quality. The assessment of academic quality must – in contrast to the results retrieved in library catalogues and subject databases – be conducted by yourself.
The academic quality of the materials is always in question.

Since general search engines only find websites accessible via links ("surface web“), they miss sources that cannot be accessed via a link or sources protected against unauthorised access (“deep web”). This is especially relevant when it comes to academic sources, since they are often listed in closed library catalogues or licenced databases. The amount of actually available webpages – and, hence, the information/literature – considerably surpasses the number of results displayed by search engines.
Scholarly literature stored in deep web cannot be found by general search engines.