When evaluating the quality of the information you are using, it is useful to identify if you are using a Primary, Secondary, or Tertiary source. By doing so, you will be able recognize if the author is reporting on his/her own first hand experiences, or relying on the views of others.
A primary source is a first person account by someone who experienced or witnessed an event. This original document has not been previously published or interpreted by anyone else.
A secondary source is one step removed from the primary original source. The author is reexamining, interpreting and forming conclusions based on the information that is conveyed in the primary source.
A tertiary source is further removed from primary source. It leads the researcher to a secondary source, rather than to the primary source.