What are media queries are and why they are used? code example

Example 1: media query

// Example media query syntax
@media only screen and (min-width: 768px) {
  .my-example-class {
    padding: 50px;
  }
}

// Best Practice
// keep default style for smallest screen size (portrait mobile, below 576px)
// and then proceed in assending order with media query like below

// Small devices (landscape phones, 576px and up)
@media (min-width: 576px) { ... }

// Medium devices (tablets, 768px and up)
@media (min-width: 768px) { ... }

// Large devices (desktops, 992px and up)
@media (min-width: 992px) { ... }

// so on ...

Example 2: media query in html style

span { background-image: url(particular_ad.png); }

@media (max-width: 300px) {
    span { background-image: url(particular_ad_small.png); }
}