Lotus Notes is the client of a collaborative

Collaborative software

Collaborative software is computer software designed to help people involved in a common task achieve goals...

 platform originally created by Lotus Development Corp. in 1989. In 1995 Lotus was acquired by IBM

IBM

International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...

 and became known as the Lotus Development division of IBM and is now part of the IBM Software Group. IBM describes the software as an "integrated desktop client option for accessing business email

Email

Electronic mail, commonly known as email or e-mail, is a method of exchanging digital messages from an author to one or more recipients. Modern email operates across the Internet or other computer networks. Some early email systems required that the author and the recipient both be online at the...

, calendars and applications on [an] IBM Lotus Domino

IBM Lotus Domino

Lotus Domino is an IBM server product that provides enterprise-grade e-mail, collaboration capabilities, and a 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...

 server." Prior to release 4.5, the term Lotus Notes referred to both the client and server applications.
Lotus Notes is a multi-user

Multi-user

Multi-user is a term that defines an operating system or application software that allows concurrent access by multiple users of a computer. Time-sharing systems are multi-user systems. Most batch processing systems for mainframe computers may also be considered "multi-user", to avoid leaving the...

 client-server

Client-server

The client–server model of computing is a distributed application that partitions tasks or workloads between the providers of a resource or service, called servers, and service requesters, called clients. Often clients and servers communicate over a computer network on separate hardware, but both...

 cross-platform

Cross-platform

In computing, cross-platform, or multi-platform, is an attribute conferred to computer software or computing methods and concepts that are implemented and inter-operate on multiple computer platforms...

 application runtime environment, it is the primary user-interface or client of the Lotus Domino/Notes suite.