IBM (Lotus) Domino is an IBM server product that provides enterprise-grade e-mail, collaboration capabilities, and custom application platform. Domino began life as Lotus Notes Server, the server component of Lotus Development Corporation's client-server messaging technology. It can be used as an application server for (Lotus) Notes applications and/or as a web server. It also has a built-in database system in the format of NSF. From release 7, Domino server can use DB2 system as its backend database.
IBM (Lotus) Notes Client is a desktop client for IBM (Lotus) Notes Domino Server. It is mainly used as an email client, but can also acts as an instant messaging client (for Lotus Sametime) and browser. It has several other roles