Bias refers to a source's purpose and point of view.
Ask yourself these questions when thinking about if a source is biased and if that bias affects its credibility:
If you are writing a research paper about cancer treatments, you will most likely need balanced, objective information.
... if you are writing an argumentative paper, you will need information about all points of view on a given topic. In this case, it's important that you recognize the bias, rather than avoid it.
Image source: "Vintage Scale Balance Balance Scale Measurement" by MamaClown is licensed under the CC0 license (public domain)
(Thank you to Tacoma Community College https://tacomacc.libguides.com/c.php?g=373171&p=2522980)
The information is from an article in a library database. Therefore, the source must be objective!
Not so fast!
Library databases may include articles from newspapers and magazines, including opinion pieces and editorials that are written from authors' personal viewpoints.
You click on the "About" section of the source's web page where it describes itself as an "unbiased non-profit" think tank. That sounds good, but that is the source writing about itself.