The difference between retail and corporate banking can be drawn clearly on the following grounds:

Retail Banking is a business model which the banks implement with the aim of acquiring maximum customer base, by offering various products and services to the individuals, and small business enterprises. Conversely, Corporate banking is another business model adopted by the banking companies so as to earn maximum revenue, by offering products and services to the business enterprises and government agencies.
Under retail banking, the products and services offered to the customers are usually standardized, also called as off-the-shelf products/services. As against, under corporate banking, customised products and services are offered to the clients, depending on their preferences and requirement.
Talking about the customer base, retail banking often brings a large customer base to the banks, whereas corporate banking does not have a large customer base but the clients are affluent.
In retail banking, the processing cost is low, whereas in the case of corporate banking there is a high processing cost.
With retail banking, one can avail loan upto Rs. 5 crores only, depending on factors like credit score, history, etc. In contrast, with corporate banking, the entities can apply for a loan more the Rs. 5 crores.
Although the volume of transactions in terms of clientele, is high in retail banking, but the value of transactions is low, because the customer base includes individuals and small businesses such as sole proprietorships, partnership firms, one-man company, etc. On the opposite side, the volume of transactions is low in corporate banking, but the value is quite high, as the client base includes business enterprises and high net worth individuals.
When it comes to profitability, corporate banking is more profitable in comparison to the retail banking division of the banks.
In a commercial bank, both retail banking and corporate banking services are provided, which differs in a number of factors including customers, products/services offered and transaction amount.

Retail banking is mass-market banking, with a large number of customers and high volume transactions. On the contrary, corporate banking, as the name itself, indicates is the services offered by the banks to the corporate houses, to help them in growing their businesses and running efficiently.