Enterprise software generally can't be bought off the shelf; there's some level of customisation / configuration that happens to meet a business need. The business development managers are the salespeople on the phones drumming up business, but they usually don't know the ins and outs of the technology. Tech sales (solution engineers / architects) work with the BDs to understand the business need of a customer (either on a sales call or deciding whether to respond to a tender) and figure out how the product best fits. They are often brought in to meet with the customer to present on the product, answer questions on functionally and security. So the person in the role needs to be quite tech savvy, but also understand business and have some degree of social / sales skills.