Sitecore Experience Platform (XP) and xConnect
xConnect is the service layer that sits in between the xDB and any trusted client that wants to read, write, or search experience data using the xConnect Client API. Communication must happen over HTTPS and the client must have the appropriate certificate thumbprint. xConnect and xDB are not interchangeable terms - they are two parts of the platform that work together.
xConnect currently has two services: Collection and Search. The following diagram demonstrates where xConnect fits into the overall XP architecture. In this diagram, Collection and Search are hosted on dedicated servers. Notice that there is no xConnect server role; Collection and Search together make up the xConnect layer:
xDB is an umbrella term for the services that are responsible for processing and storing experience data. This includes:
Reference Data service
Marketing Automation Reporting service
Marketing Automation Operations service
In a single server environment, Collection and Search can be combined into a single end point and hosted on a single server alongside two xDB services: Marketing Automation and Reference Data.
By default, xConnect implements Solr for experience search and SQL for collection. Be aware that xConnect Search and Content Search are totally separate search frameworks. You cannot use the Content Search API to access the xDB core; you must use the xConnect Client API.