Most methods in the Facebook Graph API requires an access token, or will reveal more information if the request is made using an access token.
App Access Token
Using this type of token, you can access the Facebook on behalf of your app. App access tokens then lets you posts statuses messages and similar for users that has allowed this.
Page Access Token
If a user is the administrator of a Facebook page, you can get an app access token on behalf of the user to manage that page. Page access tokens does not expire unless the user loses manage privileges to the page, changes his/her password or something similar.
User Access Token
A user access token lets you access the API on behalf on a user. The permissions of such a token is determined when the user logs in with your application. Some tokens will only live for a couple or minutes while other tokens may live for up to 60 days.
On the page below you can also find information on how to obtain a user access token on behalf of a user.