Many institutions provide such services to the public. The credibility of the institution providing the facts gives clues as to the reliability of the information. News and journalistic sites - which include national, international news, online newspapers, magazines. As in print - just because it is published does not necessarily mean it is true. Web serials that do not have ISSN numbers are probably created by entrepreneurs and less authority than other publications.
Companies are in the business of making money and acquiring and keeping customers.
They are naturally biased in favor of their own products, so watch out for inflated claims for performance and quality. Companies will not showcase their competitors' products. If you are, for example, comparing products, get impartial reviews, not company information. They serve different purposes. There are reliable and unreliable Web sites in all categories of Web sites.