what is the difference between customer and partner portal
Both systems are optimized for the audience that they serve, coming with 'canned' access to various standard objects in SF. For instance, Customer Portal does not provide the Customer Logging in with the ability to view Opportunities. Alternatively, Partner Portal licenses allow those users to do things like view Leads (which a customer would not need to do since Customers ARE leads).
The most clear difference is that Partner Portal licenses cost more than Customer Portal licenses (since partners would, presumably, be more intensive users than Customers).
A brief overview of Partner Portal...
also, some info on Customer Portal
You can find the above information by searching the Salesforce Help documentation.
Customer portal mainly for company customers where as partner portal for channels peopel that means sales people etc