Mixing: With mixing you can include or add  “a bunch of properties” from one rule-set into another rule-set.

For Example:

/* Mixing */
    border:2px solid red;


********  PARAMETERS IN MIXINS: **************

Another cool thing mixins can do is receive parameters. In the following example we add an argument for the width and height of our circles, with a default value of 25 pixels.

/* Mixing */
    border: 2px solid red;
    border-radius: 100%;
    height: @size;
    width: @size;
    margin: 10px;
    float: left;