Purdue's Online Writing Lab (OWL) is a very reliable source of help on citation & formatting.
Quick Overview: Two Types of Citations in MLA
In-Text or Parenthetical Citations
In-text citations tell your professor which source you used at a specific point in the paper. These citations also correspond to the full citation found in the "Works Cited" section at the end of your paper.
Here are four examples of in-text citations:
Works Cited Citations
The "Works Cited" section includes full citations for all sources used in your paper.