Not all companies will have a lot of information available! It depends on whether it is a 'public company' or a 'private company.' What's the difference? Public companies, or publicly-traded companies, "often referred to as reporting companies, are subject to reporting requirements and must file certain reports, including annual, quarterly, and current reports, with the SEC (Securities and Exchange Commission) on an ongoing basis." [Source: SEC] More information on public companies from Investopedia.
Private companies are 'privately held' meaning that, in most cases, the company is owned by its founders, management, or a group of private investors. [Source: Investopedia]. Private companies are not required to provide as much information as publicly-traded companies.
The subscription databases Miami University Libraries provides will have information on both public and private companies, but the depth of information will vary. The databases will tell you whether a company is public or private, but that information is also available online in freely-available sources like Wikipedia and others.