Check out example codes for "breakpoint bootstrap". It will help you in understanding the concepts better.

Code Example 1

// 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 2

--------------------------------------------------------------------------------------
Bootstrap Container Width			 					| Size        | Class Prefix
--------------------------------------------------------------------------------------
Extra small devices Phones (less than 768px)  			| None (auto) | .col-xs-
Small devices Tablets (greater than equals 768px) 		| 750px       | .col-sm-
Medium devices Desktops (greater than equals 992px)     | 970px       | .col-md-
Large devices Desktops (greater than equals 1200px)     | 1170px      | .col-lg-

Code Example 3

/* 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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