Adoption refers to a customer making a purchase then integrating that product or service into his/her daily routine.
Adoption goes beyond the purchase and specifically indicates that a customer is actively using your product or service. When implementing your offering into his/her daily routine, adoption occurs when it becomes too labor- or cost-intensive to that consumer to make a change.
Adoption provides a vital look at how useful and beneficial your products and services are for customers. When a customer cannot function — or does not want to function — without your products/services, they will forego alternatives and stick with your brand and its offerings. This is valuable not just for newly acquired customers but for early adopters who need to be reminded and informed of the benefits, features, updates, and changes within your products and services as well.
References
https://www.iedunote.com/consumer-adoption-process
https://www.finextra.com/blogposting/16911/what-you-need-to-know-about-adoption-marketing