Less is a highly dynamic stylesheet language and it extends the functionality of CSS through dynamic features and behaviors like functions, operations, mixins and variables. LESS runs on the server side such as Rhino and Node.js as well as the client side such as Firefox, Safari and Chrome.
The Variables in Less
With variables you can specify the widely used values and re-use them in the style sheet. You can also make global changes very easily simply by changing a single code line.
Mixins in Less
Perhaps the most helpful feature in Less is mixins. Basically it is a code group which you can re-use in your CSS file. This allows you to edit just once to ensure that the changes would be reflected everywhere. Mixins will also allow users to embed all properties from one class into another easily along with the class name as well as its properties. Mixins will also behave much like functions and will be able to take arguments.
Nested Rules in Less
Instead of building longer selector names for specifying inheritance you can just nest the selectors inside the other selectors. This makes the style sheets short and inheritance clear. It also includes Operations which will allow you to multiply, divide, subtract and add the property values as well as colors. This will allow you to create various complex property relationships. Operations must be performed only in parentheses to ensure CSS compatibility.
This feature provides an easy way to develop Less and get started with it. It is particularly helpful for production and when performance is important. Client side also includes the Watch Mode feature which allows your styles to be automatically refreshed when they are changed.