Core Roles and non-core Roles

Content Delivery functionality consists of a number of Roles. A Role is (the Content Delivery side of) a product feature. We distinguish between core Roles, which are always needed to get the product up and running, and non-core Roles, which you may or may not install based on business needs.

Core Server Roles

The core Content Delivery Roles are:
RoleDescription
Discovery ServiceExposes the Discovery Endpoint, through which all Content Delivery services are made available.
Content ServiceExposes a number of core Content Delivery APIs for the presentation environment to interact with.
Session-enabled Content ServiceUsed instead of the Content Service in a Content Delivery environment that supports Experience Manager.
Content DeployerDeploys content published from Content Manager.
PreviewEnables the Content Delivery functionality of Experience Manager.

Nonessential Server Roles

The nonessential Server Roles are:
Server RoleDescription
Context EngineEnables the discovery of, and ability to respond to, contextual information about the visitors of your website, and about the devices they use.
Contextual Image DeliveryEnables request-time image transformation on the published website.
Context Expression ExtensionMakes campaign management and analysis data available for use on your SDL Tridion Sites-based website. To use the Context Expression Extension, you must have the add-on product SDL DXA set up, and specifically the Context Expression Module of that product.