Multi-Tier Architecture, also known as multi-layered architecture, is a software design pattern that organizes an application into logically and physically separate tiers, each responsible for a specific set of tasks. This architectural style promotes modularity, scalability, maintainability, and security by decoupling the different parts of an application.

At a high level, a multi-tier architecture typically consists of three or more tiers:

1. Presentation Tier – Also known as the user interface layer, this is the front-end of the application where users interact with the system. It handles the display of information and captures user inputs. This tier is commonly built using web technologies such as HTML, CSS, and JavaScript.

2. Application Tier (Logic Tier) – This middle layer contains the core functionality of the application, including business rules, decision logic, and data processing. It acts as a mediator between the presentation and data tiers. This is often developed using server-side languages like Java, Python, C#, or Node.js.

3. Data Tier – This is the backend layer responsible for managing data persistence. It includes databases and data storage systems that handle queries, updates, and data integrity. Common technologies here include relational databases like PostgreSQL, MySQL, or Oracle.

Some implementations extend this model to include additional tiers, such as service tiers (for APIs or microservices), caching tiers, or integration layers for communication with external systems.

Benefits of Multi-Tier Architecture include improved separation of concerns, which allows teams to develop, update, and scale each tier independently. It also enhances security by restricting access to the data layer and improves flexibility by allowing different technologies to be used in each tier.

This architectural approach is widely used in enterprise applications, web services, and distributed systems. For example, an e-commerce website might use the presentation tier for the online storefront, the application tier to handle transactions and pricing logic, and the data tier to store product and customer information.

However, designing and maintaining a multi-tier system can introduce complexity, particularly in deployment, testing, and communication between layers. Proper orchestration and architecture planning are key to harnessing its advantages without excessive overhead.