Retail literally means "The sale of goods or commodities in small quantities directly to consumers."
"Sales" on the other hand, can refer to the sale of just about anything to anyone. IN general, it relates to the sale of items or services to businesses.
That is, the sale of an ipod to a customer in a Apple store = retail
The sale of a copier to a a business would probably be considered Sales.
Also, retail jobs are generally low paying jobs for teens and the uneducated.
Sales jobs can be extremely high paying, and may require specialized experience and a related degree (i.e., my buddy sells servers for IBM, and they require 5 years fo sales experience and a BS in computer science for the job, but he also makes $150k+ per year)