Monolithic architecture is a traditional software design pattern in which an entire application is built as a single, unified unit. In a monolithic system, the application’s user interface, business logic, and data access layers are tightly coupled and operate as a single entity. All of the code is compiled and deployed together, which means any change to a part of the system requires rebuilding and redeploying the entire application.

The monolithic architecture has its benefits, such as simplicity in development and testing for smaller projects, and it's easier to set up initially. However, as the system grows, this architecture can become cumbersome due to its lack of flexibility and scalability. It can lead to issues such as tight coupling, where changes in one part of the system affect the entire application, making it harder to scale or update components independently.

Monolithic applications are also harder to scale horizontally compared to microservices architecture, which divides the application into smaller, independently deployable services. Despite its challenges, some legacy systems and small-scale applications still rely on monolithic architecture due to its ease of development and straightforward deployment.