Buttons
Examples
Bootstrap includes six predefined button styles, each serving its own semantic purpose.
Outline buttons
In need of a button, but not the hefty
                                            background colors they bring? Replace the default modifier classes with
                                            the .btn-outline-* ones to remove
                                            all background images and colors on any button.
Rounded Buttons
Add .btn-rounded class in <button> tag for a rounded button.
Default button
Outline Rounded button
Button tags
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).
Sizes
Fancy larger or smaller buttons? Add
                                            .btn-lg or .btn-sm for additional sizes.
                                        
Large button
Small button
Block Buttons
Create block level buttons—those that
                                            span the full width of a parent—by adding .btn-block.
Toggle states
Add data-toggle="button"
                                            to toggle a button’s active
                                            state. If you’re pre-toggling a button, you must manually add the .active class
                                            and aria-pressed="true" to the
                                            <button>.
                                        
Button addons
Button Group
Group a series of buttons together on a single line with the button group
Basic example
Button toolbar
Vertical variation
Checkbox-Radio buttons
Bootstrap’s .button styles 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-group containing those
                                            modified buttons to enable toggling in their respective styles.