What is Less
Less is a CSS pre-processor that facilitates you to customize, manage and reuse the style sheets for the webpage. Less is an extension of CSS and a dynamic style sheet language which can be run on client side or server side.
Less is an open source language. It is also cross browser compatible.
What is CSS Preprocessor
CSS preprocessor is a scripting language that is an extension of CSS. It is compiled into regular CSS syntax and then the CSS is read by the web browser. Less looks very similar to CSS but it provides functionalities like variables, functions, mixins and operations etc that facilitates you to build dynamic CSS.
Less and SASS both are the example of CSS preprocessor because both are compiled and produce CSS syntaxes that are read by the web browser.
How to use
Less is written in JavaScript and requires either Node.js or web browser to run. You can include Less.js in your web site and it can compile all the linked .Less style sheets in real time, but this is slow and is not recommended.
Here we are using Node.js as a graphical program to compile Less style sheets and deploy regular CSS file. The reason behind using Node.js is that it is very fast and impressive.
History of Less
Less was first written in Ruby but later versions were written in JavaScript and Ruby was deprecated. Less was designed and written by Alexis Sellier in 2009.