Leaving aside the obvious difference between the two, in-store merchandising and digital merchandising are very similar disciplines with shared goals.
In-store merchandisers work to promote products in line with weekly and monthly trade results and longer-term sales strategies. Online merchandisers do exactly the same and work in a similar fashion to their offline counterparts, organizing, discounting, and combining products in both novel and traditional ways to encourage conversions amongst their customers.
Think about how in-store merchandisers place items often bought together in the same physical space and combine this with exposure to suggestive products to generate cross-sell opportunities, and then how digital merchandisers use the same techniques to recommend products to encourage wider and deeper forays into product catalogs.
Promotion is at the very heart of personalization, which uses a data-driven approach to suggest products and services that are most likely to resonate with shoppers. Beyond using product recommendations, simple techniques such as hero banners and product badging are used to promote new products and services, highlight discounts, and encourage shoppers to explore a product catalog.
Beyond these techniques, practical applications of the wisdom of crowds theory through stock counters, trending notifications, and last purchased notifications provide confidence in purchasing decisions and encourage shoppers to convert for fear of missing out or for not being part of the latest trends.