Ubiquitous computing refers to computers integrated into everyday objects and environments. It is the next wave after desktop computing and aims to make many computers available throughout the environment, serving each person, but doing so invisibly. A key researcher who coined the term was Mark Weiser at Xerox PARC in the 1980s. Experiments included tabs, pads and boards, and applications now include smart devices, interactive displays, and augmented reality games. Challenges include designing for privacy, security, and seamless interactions across contexts.