Cloud infrastructure in web applications refers to the collection of hardware and software resources that provide cloud computing services over the internet. This infrastructure typically includes servers, storage, networking, and virtualization resources, all hosted in a cloud provider's data centers. In a cloud environment, these resources are dynamically allocated and managed, offering flexibility and efficiency that traditional on-premises infrastructures cannot match. Web applications leverage cloud infrastructure for various purposes, such as hosting, storage, computing power, and other essential services, enabling them to scale resources up or down based on demand.

Important qualities in cloud infrastructure are Automation, Security and Cost control. Automation plays a crucial role in streamlining processes, enabling the automatic provisioning and management of resources, reducing manual intervention, and improving efficiency. Security is paramount, involving robust measures to protect data, applications, and infrastructure from potential threats. Scalability ensures that the infrastructure can seamlessly handle increasing workloads without compromising performance. Cost control and efficiency are also essential qualities, emphasizing the need for optimized resource allocation to prevent unnecessary expenses and ensure that the cloud infrastructure aligns with budgetary constraints. A well-designed cloud infrastructure balances these qualities, providing a reliable, secure, scalable, and cost-effective foundation for web applications.