Two-Tier Architecture:

A two-tier architecture, also known as a client-server architecture, consists of two main layers: a client layer and a server layer. The client layer is responsible for interacting with the user and presenting data to them, while the server layer is responsible for processing requests and managing the application's data and business logic.

In a two-tier architecture, the client layer communicates directly with the server layer. This can result in a simpler and more efficient system, but can also make it more difficult to scale and maintain as the application grows.

Three-Tier Architecture:

A three-tier architecture, also known as a multi-tier architecture, consists of three main layers: a presentation layer, an application layer, and a data layer. The presentation layer is responsible for interacting with the user and presenting data to them, the application layer is responsible for processing requests and managing the application's business logic, and the data layer is responsible for managing the application's data.

In a three-tier architecture, each layer communicates with the layer directly above or below it. This can make the system more complex, but also more flexible and easier to maintain and scale as the application grows.

Normalization:

Normalization is a technique used in database design to eliminate redundancy and improve data integrity. It involves organizing data into tables and ensuring that each table has a unique primary key and that all other attributes in the table depend on that key. This helps to ensure that data is consistent and accurate and reduces the risk of errors or inconsistencies in the data.

Normalization is typically achieved through a series of steps or "normal forms," with each normal form building on the previous one. The most commonly used normal forms are first normal form (1NF), second normal form (2NF), and third normal form (3NF), although there are higher levels of normalization as well.

In summary, two-tier and three-tier architectures are types of system architectures used in software development, with three-tier architectures consisting of three main layers and two-tier architectures consisting of two. Normalization is a technique used in database design for eliminating redundancy and improving data integrity, accomplished through organizing data into tables and ensuring each table has a unique primary key and all other attributes depend on that key._