What is basic difference between sales, marketing and promotion?

Sales is the action of selling the product to customers.Marketing is to define and advertise the product to attract more consumers.Promotion is to make the product available everywhere and at any instance.

The basic idea is not about pointing out the difference, its about the relation between these three essentials. 

Marketing:

You create the awareness, you find out the needs of the market and explain the market what your product is. It is the strategy that will identify your sales.

Sales: 

Its about make the product to sell at consumer's doorstep, it means that you will have the conformation that you have received the payment. You execute the marketing ideas and strategies.

Promotion:

Making the product known to the consumers or keep them reminding about the product is promotion, through ads, and other mediums of promotion.