And it becomes interesting when, with all due respect, the so-called experts, having built their careers in the relevant fields, seemed rather confused between the functioning and mandate of 'Business Development' and 'Sales' functions. Before taking a dig on that, respectfully, here is my version of the 'classical' definition (or differentiation) of the two:
"Business Development is a bunch of activities of today, based on your strategic vision of your product/service framework, that the Sales people would be selling tomorrow."Well, this definition might neither be universal nor be entirely technically accurate. However, it does give a certain level of clarity (when some of the rather experienced folks are contributing to the confusion). To me, these two functions are neither the 'same' nor 'interchangeable', but are distinct. And by the virtue of that clarity one can perhaps define both the functions more accurately and also appreciate their imperatives.
So, what we are saying here is - today's Business Development initiatives could (should) potentially translate into sales targets of tomorrow - in other words: Sales follows Business Development. And thus, what we call pre-sales will have to fit between the two where it would have a sort of a 'vetting' role for the tasks trickling down from BD for the Sales to be made. It perhaps is a different matter that all of these three functions may not exist independently for a given organization, but could be merged among each others (pre-sales may be merged with BD, or BD may be made to co-exists in the same basket as of Sales. And that perhaps is the very reason where the confusion about the distinction is arising from).
[Above: The 'Arrow-head' components: a) the Sales function as the cutting-edge, b) the Business Development (BD) function, the main-body, that gives the aerodynamic shape and (thus) 'direction' to the arrow, and c) the Pre-sales function that embeds the Arrow-head to the stem (delivery streams).]
My personal exposure to these "cutting-edge" functions has been in terms of IT systems services, products, and delivery (where I have had the opportunity to performed all the roles except for direct-sales). In terms of the required skill-sets and experience for each of these functions: a BD professional might have to have a more strategic (and, if I may add, visionary) inclination on top of pure selling skills. A pre-sales professional, at the same time, may have to have a more Risk-oriented outlook (the correct Risk-appetite measure, as well as Risk-averse functioning) and the mandate to have Risk-mitigation embedded within the Sale that is going to be made. This is also the position where the 'Analysis' bit could play its role. And connect the "arrow-head" to the structural strength of the stem (delivery streams) which provides for the momentum for the 'travel' (i.e. growth).
Further, this also helps give the logical alignment of each of these functions vis-a-vis the leadership roles in a typical organization. The BD function should ideally be with the top executive leadership (CEO/COO); the Sales function should report into BD; and the pre-sales should be closely knit with delivery/operations and having a dotted-line reporting to the executive leadership.
Go here for the interesting 'confusion' that I referred to at the beginning (you may would want to skip the vanity of the thread at the start and move over to the answers).