Application modernization is the process of updating or transforming legacy software applications to improve their functionality, performance, and scalability, and to better align with modern business needs and technology trends. The primary goal of application modernization is to extend the lifespan of legacy applications by making them more efficient, secure, and flexible, while reducing their maintenance and operating costs.

There are several approaches to application modernization, including:

1. Replatforming - migrating the application to a new platform, such as a cloud-based platform, to take advantage of modern architecture and infrastructure.
2. Refactoring - redesigning and restructuring the application's code to improve its performance, scalability, and maintainability, without changing its functionality.
3. Rehosting - moving the application to a new hosting environment, such as a virtual machine or container, to improve its scalability and flexibility.
4. Re-architecting - redesigning the application's architecture to take advantage of modern development practices, such as microservices or containerization.
5. Rebuilding - completely rebuilding the application from scratch using modern development tools and practices.

Application modernization can help businesses reduce their IT costs, improve their agility and flexibility, and better meet the changing needs of their customers and users. It can also help organizations stay competitive in today's rapidly evolving technology landscape.