Open web sources can be searched, typically using search engines such as Google, and are available on the internet without requiring authentication (such as user name & password, or a payment being made).
Because anyone can publish anything online, it is very important to take extra time evaluating resources you find when searching the open web.
Video clip via CSPAN Classroom, recorded March 6, 2019.
Research, technical, and statistical reports that are not formally published as books, journal articles, or in a formal manner by commercial publishers fall into the category of "grey literature." They are sometimes hard to find, but think-tanks, lobbying groups, government agencies and inter-governmental organizations often post this type of report on their websites.
"Think tanks are public-policy research analysis and engagement organizations that generate policy-oriented research, analysis, and advice on domestic and international issues, thereby enabling policymakers and the public to make informed decisions about public policy. Think tanks may be affiliated or independent institutions that are structured as permanent bodies, not ad hoc commissions. These institutions often act as a bridge between the academic and policymaking communities and between states and civil society, serving in the public interest as independent voices that translate applied and basic research into a language that is understandable, reliable, and accessible for policymakers and the public." -- Think Tanks & Civil Societies Program, Univiersity of Pennsylvania