Bootstrap includes six predefined button styles, each serving its own semantic purpose.
                                    Replace the default modifier classes with the .btn-outline-*ones to remove all background images and colors on any button.
                                
                                    Use class .btn-roundedfor button round border.
                                
                                    Use class .btn-roundedfor button round border.
                                
                                    Add .btn-lgor .btn-smfor additional sizes.
                                
                                    Add .w-xs, .w-sm, .w-mdand .w-lgclass for additional buttons width.
                                
                                    The .btn classes are designed to be used with the <button>element. However, you can also use these classes on <a>or <input>elements (though some browsers may apply a slightly different rendering).
                                
                                    Add data-toggle="button" to toggle a button’s active state. If you’re pre-toggling a button, you must manually add the .activeclass andaria-pressed="true"to the <button>.
                                
                                    Create block level buttons—those that span the full width of a parent—by adding .btn-block.
                                
                                    Bootstrap’s .buttonstyles can be applied to other elements, such as <label>s, to provide checkbox or radio style button toggling. Add data-toggle="buttons"to a .btn-groupcontaining those modified buttons to enable toggling in their respective styles.
                                
                                    Wrap a series of buttons with .btnin .btn-group.
                                
Combine sets of button groups into button toolbars for more complex components. Use utility classes as needed to space out groups, buttons, and more.
                                    Instead of applying button sizing classes to every button in a group, just add .btn-group-*to each .btn-group, including each one when nesting multiple groups.
                                
Make a set of buttons appear vertically stacked rather than horizontally. Split button dropdowns are not supported here.