Customer service encompasses all the human resources and organizational structures deployed to respond to customer requests for information and services before, during, and after a purchase. While often associated with after-sales service or customer support, it can also intervene before the purchase itself. The missions of customer service vary depending on the sector, with some focusing on pre-purchase inquiries while others concentrate on post-sales support.

The communication channels managed by customer service departments are diverse, with a growing predominance of digital channels in response to evolving consumer behavior. This has led to a shift from traditional call centers to customer contact or interaction centers. Despite this evolution, the telephone remains a major means of contact, succeeding postal mail in the history of customer service. Common channels include telephone, email, social media, live chat, chatbots, postal mail, and face-to-face meetings, which are often overlooked in the traditional view of customer support.

In 2017, the BVA annual Customer Service Observatory delivered key data on industry trends, while a Harris Interactive study, commissioned by Butagaz, explored the role of customer service as customer support.