Any time your work contains or refers to someone else's:
you need to include a citation.
In-line citations or foot/endnotes (depending on the assigned citation style) should be inserted at the point of use in your assignment and indicate that the information you just presented came from a source other than your own brain or common knowledge.
A Bibliography and/or Works Cited section should be included at the end of your assignment.
Lists all the outside works you read or considered for this assignment
Lists all the works you referred to with formal citations (in-line or foot/end notes) in the body of your assignment
There are hundreds of bibliographic styles, each with it's own precise formatting. The most popular at CapU are MLA and APA.