Explain the different button sizes.

Button Sizes

Bootstrap provides four button sizes:

Large, Medium, Small, Xsmall

The classes that define the different sizes are:
• .btn-lg
• .btn-md
• .btn-sm
• .btn-xs

 Structure

 <button type="button" class="btn btn-primary btn-lg">Large</button> 
<button type="button" class="btn btn-primary btn-md">Medium</button>
 <button type="button" class="btn btn-primary btn-sm">Small</button>
 <button type="button" class="btn btn-primary btn-xs">XSmall</button>