UI (User Interface) is the visual and interactive design of a product; it's the way how users interact with the product. On the other hand, UX (User Experience) is the overall experience and satisfaction of the user with the product; it's the feeling users have when they interact with the product, which is influenced by UI and other factors such as performance, accessibility, and content. UI and UX play critical roles in digital product design and development, aiming to create easy-to-use, efficient and satisfying products.

Front-end web development is the process of building and designing user-facing parts of websites and web applications using HTML, CSS, and JavaScript. It is a crucial aspect of web development that focuses on creating interactive and visually appealing interfaces for users to interact with. They use various tools and technologies, such as web frameworks, libraries, and development frameworks, to help them create and maintain efficient, high-quality code. Additionally, they test and debug their code to ensure it works correctly across different browsers and devices.

Back-end web development is the process of building and designing the server side of web applications and websites. It involves the creation of server-side logic, database management, and integration of the front end with the back end. Back-end developers are responsible for creating and maintaining the web application's functionality, including server-side scripts. They use a variety of programming languages, such as Java, Python, Ruby, PHP, and C#, to create the back-end logic and database connections.

Servers are hardware devices that handle and respond to HTTP requests from web clients, such as web browsers. They are responsible for hosting and serving web pages and other files over the internet. Popular web servers include Apache, Nginx, and Microsoft IIS. They process the incoming requests, usually using a specific protocol such as HTTP or HTTPS, and then return a response to the client. Web servers can be configured to serve static files like HTML, CSS, and JavaScript or dynamic content generated by programming languages like PHP or Python.

DNS (Domain Name System) is a system that translates domain names, such as www.example.com, into IP addresses that computers use to locate and connect to web servers.

SSL (Secure Sockets Layer) is a security protocol that encrypts the data transmitted between a web server and a client, such as a web browser. It uses a public key infrastructure to establish a secure connection and prevent sensitive information, such as login credentials and financial data, from being intercepted by malicious actors.

APIs (Application Programming Interfaces) are a set of protocols, routines, and tools that allow different software systems to interact with one another. They provide a way for other applications to communicate and exchange data, enabling them to work together seamlessly. APIs are commonly used to connect different applications, such as web applications, mobile apps, or back-end systems. They can access data from external sources, such as social media platforms, weather services, payment systems, etc.