Back-end development involves building the server-side logic, databases, and server infrastructure that support the functionality and data processing of a website or web application. It typically involves using the following programming languages and technologies:

1. Python: Python is a versatile and widely used programming language known for its simplicity, readability, and extensive libraries and frameworks. Popular Python frameworks for back-end development include Django and Flask, which provide tools for building web applications, handling HTTP requests, interacting with databases, and implementing security features.

2. JavaScript (Node.js): JavaScript is a versatile programming language used for both front-end and back-end development. Node.js is a runtime environment that allows developers to run JavaScript code on the server-side. Node.js is commonly used for building scalable and high-performance web applications, APIs, and real-time applications.

3. Java: Java is a robust, platform-independent programming language commonly used for building enterprise-level web applications and back-end systems. Java frameworks such as Spring and Hibernate provide tools for building scalable, secure, and maintainable web applications, handling database operations, and implementing business logic.

4. Ruby: Ruby is a dynamic and expressive programming language known for its simplicity and productivity. Ruby on Rails (Rails) is a popular web application framework built on top of Ruby, providing tools for rapid development, convention over configuration, and building RESTful APIs and web services.

5. PHP: PHP (Hypertext Preprocessor) is a server-side scripting language widely used for building dynamic web applications and websites. PHP frameworks such as Laravel, Symfony, and CodeIgniter provide tools for building scalable, secure, and feature-rich web applications, handling user authentication, and interacting with databases.

6. C#: C# (C Sharp) is a powerful and modern programming language developed by Microsoft, commonly used for building web applications, APIs, and enterprise-level systems. ASP.NET is a popular web application framework for building scalable, secure, and high-performance web applications using C#.

7. Go (Golang): Go is a statically typed, compiled programming language developed by Google, known for its simplicity, efficiency, and concurrency support. Go is commonly used for building scalable and high-performance web servers, microservices, and distributed systems.

8. Scala: Scala is a modern, functional, and object-oriented programming language that runs on the Java Virtual Machine (JVM). Play Framework is a popular web application framework for building scalable and reactive web applications using Scala and Java.

In addition to these programming languages, back-end developers often use database management systems (DBMS) such as MySQL, PostgreSQL, MongoDB, and SQL Server to store and manage data, as well as web servers such as Apache HTTP Server, Nginx, and Microsoft Internet Information Services (IIS) to serve web applications to users. By leveraging these programming languages and technologies, back-end developers can build scalable, secure, and feature-rich web applications and systems that meet the needs of modern web users.