Hi Abhishek, In addition to what sfdcjoey mentioned, there is differences in terms of data that can be stored, number of active users, number of apps etc. The complete comparison is available at https://help.salesforce.com/apex/HTViewHelpDoc?id=limits_general.htm&language=en_US
Developer is Free Edition and Enterprise has price per User.
http://www.salesforce.com/in/crm/editions-pricing.jsp
In addition to what sfdcjoey mentioned, there is differences in terms of data that can be stored, number of active users, number of apps etc. The complete comparison is available at
https://help.salesforce.com/apex/HTViewHelpDoc?id=limits_general.htm&language=en_US