Security token
Question:
Answer:
You need to enter your Salesforce user name, password and security token to get connected to Salesforce. You have to set this on Activation settings.
Salesforce.com security settings require you to use the security token along with your password to login from 3rd party applications using web service APIs.
Here is some information on how to get it :
https://help.salesforce.com/HTViewHelpDoc?id=user_security_token.htm