An Informational score is a test result which doesn’t return a numeric score (i.e. a score from 0 to 10), but instead appears as a purple “i” or “info” for information.
Informational scores exist to tell you something, but they don’t score you based on it.
Examples include the Contact details test, which presents useful information (what your contact details are) but does not score you based on this information. Generally Informational scores appear where you could not be reasonably expected to influence the result of a test (e.g. Typosquatting test) or where Sitebeam could not be expected to consistently score sites accurately based upon it (e.g. Outgoing links test).