Check out example codes for "media query breakpoints". It will help you in understanding the concepts better.

Code Example 1

// Best Practice suggests
// 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 above till next break point)
@media (min-width: 576px) { ... }

// Medium devices (tablets, 768px and above till next break point)
@media (min-width: 768px) { ... }

// Large devices (desktops, 992px and above till next break point)
@media (min-width: 992px) { ... }

// so on ...

Code Example 2

/* Mobile first, baby! */
/* Medium devices (landscape tablets, 768px and up) */
@media only screen and (min-width: 768px) {}
/* Large devices (laptops/desktops, 992px and up) */
@media only screen and (min-width: 992px) {}
/* Extra large devices (large laptops and desktops, 1200px and up) */
@media only screen and (min-width: 1200px) {}

Code Example 3

// Extra small devices (portrait phones, less than 576px)
// No media query for `xs` since this is the default in Bootstrap

// 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) { ... }

// Extra large devices (large desktops, 1200px and up)
@media (min-width: 1200px) { ... }

Code Example 4

/* Extra small devices (phones, 600px and down) */
@media only screen and (max-width: 600px) {}

/* Small devices (portrait tablets and large phones, 600px and up) */
@media only screen and (min-width: 600px) {}

/* Medium devices (landscape tablets, 768px and up) */
@media only screen and (min-width: 768px) {}

/* Large devices (laptops/desktops, 992px and up) */
@media only screen and (min-width: 992px) {}

/* Extra large devices (large laptops and desktops, 1200px and up) */
@media only screen and (min-width: 1200px) {}

Code Example 5

// Extra small devices (portrait phones, less than 576px)
@media (max-width: 575.98px) { ... }

// Small devices (landscape phones, 576px and up)
@media (min-width: 576px) and (max-width: 767.98px) { ... }

// Medium devices (tablets, 768px and up)
@media (min-width: 768px) and (max-width: 991.98px) { ... }

// Large devices (desktops, 992px and up)
@media (min-width: 992px) and (max-width: 1199.98px) { ... }

// Extra large devices (large desktops, 1200px and up)
@media (min-width: 1200px) { ... }

Code Example 6

/* Answer to: "bootstrap media queries" */

/*
  Since Bootstrap is developed to be mobile first, the use a handful
  of media queries to create sensible breakpoints for their layouts
  and interfaces. These breakpoints are mostly based on minimum
  viewport widths and allow scaling up elements as the viewport
  changes.

  Bootstrap primarily uses the following media query ranges—or
  breakpoints—in their source Sass files for their layout, grid system,
  and components.
*/

/* Extra small devices (portrait phones, less than 576px) */
/* No media query for `xs` since this is the default in Bootstrap */`32`

/* 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) { ... }

/* Extra large devices (large desktops, 1200px and up) */
@media (min-width: 1200px) { ... }

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