Cloud computing is the delivery of computing services, including storage, processing power, databases, networking, and software, over the internet, or "the cloud." It allows individuals and businesses to access and use resources without the need for physical hardware or local servers. Cloud computing is scalable, meaning resources can be increased or decreased as needed, and it offers flexibility and cost efficiency since users only pay for what they use. 

Cloud services are typically categorized into three models: Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS). Major cloud service providers, such as Amazon Web Services (AWS), Microsoft Azure, and Google Cloud, offer various tools and platforms for storage, data analytics, machine learning, and application hosting. Cloud computing is essential for modern businesses due to its accessibility, scalability, and ability to facilitate collaboration and innovation across remote teams.