Cloud computing provides on-demand access to IT resources and applications from the Internet. There are different deployment models (public, private, hybrid, community clouds) and service models (IaaS, PaaS, SaaS). IaaS provides fundamental computing resources, PaaS provides platforms for developing and deploying applications, and SaaS provides software applications delivered as an online service. Cloud computing offers advantages like reduced costs, improved performance and collaboration, but also disadvantages like requiring an Internet connection and potential security issues.