What they are: Documents created by particular organizations, reporting on particular issues.
What they give you: Basic facts about an issue, and analysis of that issue.
Note: Some reports are neutral, but not all of them are. If a report argues for one side of a controversial issue, it's up to you to evaluate the argument and respond to it.
How to spot them:
What they look like in library search results:
(Note that there's no "Report" icon, so they show up with some other icon, usually "Book" or "Journal.")
What they look like online (in PDF format, as is typical):
What they look like in print: