'Scalability' in web development is about a system, network, or process's capability to manage increasing workloads or its potential for expansion to accommodate growth. For web applications, being scalable is essential to manage higher loads, such as more users, data, or transactions, without degrading performance.

There are two main approaches to achieving scalability: vertical scaling involves enhancing the existing infrastructure (like upgrading a server), while horizontal scaling entails adding more nodes to the system (such as incorporating additional servers). Web applications need to be designed with scalability in focus, ensuring effective distribution of workload and resources as the demand grows.

Scalable web architectures often utilize cloud services, load balancing, distributed databases, and microservices to handle substantial traffic and data volumes. Scalability also encompasses aspects of maintainability, cost-efficiency, and the ability to upgrade systems with minimal interruption.

Scalability is vital for businesses expecting growth in their user base or data volume, as it helps maintain consistent service quality and performance over time. It is a key component of contemporary web application design and architecture.

In summary, scalability is an integral characteristic of web applications and infrastructure, ensuring they continue to perform reliably as they expand and face increasing usage. It involves various strategies and technologies that enable systems to adapt and grow with their user and data demands.