Referral source is from where they heard about the company.
Contact point is how the client contacted you ( Eg: Display home ). This is the place where the first contact was made with the company.
These are the standard referral types
Contact Point is relevant to Display home, Sales team and Business process referral types
Referral Source is relevant to Advertising or Sales team referral type
Referral Sources can be set up from the following screen
Based on the referral types selected, the data shows in contact point and referral sources dropdown. This can be see in the Lead Details screen