LEMP stack refers to Linux, Nginx(Engine-X), MySQL, and PHP. Usually used in modern web development with its powerful lightweight Nginx server’s features.
Linux is a system Kernel act as the bridge between Operating System and Hardware. Ubuntu is a Linux based Operating System which is often used for setup LEMP stack environment.
Nginx( Engine-X) is a web server runs on Linux. It is highly optimized, lightweight and fast server. Most of the time Nginx is chosen as a web server as it is more easy for configuration.
MySQL is mainly used for structured data management and storage. One of the most popular, widely used and best Relational Database Management System (RDBMS) being used for in modern web application development.
PHP also refers as Hypertext Preprocessor is server-side language, runs efficiently, most widely used and community-driven language. It can run on various platforms (etc. Linux), compatible with almost all servers (etc. Nginx), and support a wide range of databases systems.