Quote from Wikipedia:
Presales will become a key competitive differentiator for the demand-driven economy.
Presales is the activity that qualifies in or out a prospect. Such an engagement with a prospect starts from the first point of interaction until an outcome has been reached. These interactions can be started through a variety of engagement triggers such as direct marketing, email and SMS campaigns, interactive advertising, online ads, portals and online billing.
A positive presales outcome is the generation of a warm lead or the trigger of a transactional event. However, the highest value of presales interactions is to understand why a positive outcome has not been reached. The aggregation of these interactional patterns can show the emergence of unmet and latent demand.
Presales is a relevant method for when there is a multiplying of choices for the prospect to consider. The diversity of pathways leading to different outcomes can be significant for complex products and services or when engaging with cross-sell and up-sell interactions.
I hope I know more in this area. But I don't. I think presales is part of the product management process. Even product management have different meanings and approach for different companies.