<div class="btn-group">
  <button type="button" class="btn btn-default">Left</button>
  <button type="button" class="btn btn-default">Middle</button>
  <button type="button" class="btn btn-default">Right</button>
</div>

 Standard button
<button type="button" class="btn btn-default">Default</button>

Provides extra visual weight and identifies the primary action in a set of buttons
<button type="button" class="btn btn-primary">Primary</button>

Indicates a successful or positive action
<button type="button" class="btn btn-success">Success</button>

Contextual button for informational alert messages
<button type="button" class="btn btn-info">Info</button>

Indicates caution should be taken with this action
<button type="button" class="btn btn-warning">Warning</button>

Indicates a dangerous or potentially negative action
<button type="button" class="btn btn-danger">Danger</button>

  <button type="button" class="btn btn-default btn-lg">Default button</button>
  <button type="button" class="btn btn-primary btn-lg">Primary button</button>
  <button type="button" class="btn btn-primary btn-lg btn-success">Success button</button>
  <button type="button" class="btn btn-primary btn-lg btn-info">Info button</button>
  <button type="button" class="btn btn-primary btn-lg btn-warning">Warning button</button>
  <button type="button" class="btn btn-primary btn-lg btn-danger">Danger button</button>

  <button type="button" class="btn btn-default">Default button</button>
  <button type="button" class="btn btn-primary">Primary button</button>
  <button type="button" class="btn btn-primary btn-success">Success button</button>
  <button type="button" class="btn btn-primary btn-info">Info button</button>
  <button type="button" class="btn btn-primary btn-warning">Warning button</button>
  <button type="button" class="btn btn-primary btn-danger">Danger button</button>

  <button type="button" class="btn btn-default btn-sm">Default button</button>
  <button type="button" class="btn btn-primary btn-sm">Primary button</button>
  <button type="button" class="btn btn-primary btn-sm btn-success">Success button</button>
  <button type="button" class="btn btn-primary btn-sm btn-info">Info button</button>
  <button type="button" class="btn btn-primary btn-sm btn-warning">Warning button</button>
  <button type="button" class="btn btn-primary btn-sm btn-danger">Danger button</button> 

  <button type="button" class="btn btn-default btn-xs">Default button</button>
  <button type="button" class="btn btn-primary btn-xs">Primary button</button>
  <button type="button" class="btn btn-primary btn-xs btn-succes">Success button</button>
  <button type="button" class="btn btn-primary btn-xs btn-info">Info button</button>
  <button type="button" class="btn btn-primary btn-xs btn-warning">Warning button</button>
  <button type="button" class="btn btn-primary btn-xs btn-danger">Danger button</button>

<div class="btn-group">
  <button type="button" class="btn btn-default">1</button>
  <button type="button" class="btn btn-default">2</button>

  <div class="btn-group">
    <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown">
      Dropdown
      <span class="caret"></span>
    </button>
    <ul class="dropdown-menu">
      <li><a href="#">Dropdown link</a></li>
      <li>>a href="#">Dropdown link</a></li>
    </ul>
  </div>
</div>

 
 <div class="btn-group">
  <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown">
    Action <span class="caret"></span>
  </button>
  <ul class="dropdown-menu">
    <li><a href="#">Action</a></li>
    <li><a href="#">Another action</a></li>
    <li><a href="#">Something else here</a></li>
    <li class="divider"></li>
    <li><a href="#">Separated link</a></li>
  </ul>
 </div>

<div class="btn-group">
  <button type="button" class="btn btn-default">Action</button>
  <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown">
    <span class="caret"></span>
  </button>
  <ul class="dropdown-menu">
    <li><a href="#">Action</a></li>
    <li><a href="#">Another action</a></li>
    <li><a href="#">Something else here</a></li>
    <li class="divider"></li>
    <li>><a href="#">Separated link</a></li>
  </ul>
</div>

<div class="btn-group dropup">
<button type="button" class="btn btn-default">Dropup</button>
<button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown"><span class="caret"></span></button>
<ul class="dropdown-menu">
<li><a href="#">Action</a></li>
<li><a href="#">Another action</a></li>
<li><a href="#">Something else here</a></li>
<li class="divider"></li>
<li><a href="#">Separated link</a></li>
</ul>
</div>

<div class="row">
  <div class="col-lg-6">
    <div class="input-group">
      <span class="input-group-btn">
        <button class="btn btn-default" type="button"><i class="fa fa-search"></i></button>
      </span>
      <input type="text" class="form-control">
    </div>
  </div>
  <div class="col-lg-6">
    <div class="input-group">
      <input type="text" class="form-control">
      <span class="input-group-btn">
        <button class="btn btn-default" type="button"><i class="fa fa-search"></i></button>
      </span>
    </div>
 </div>
</div>

<div class="row">
  <div class="col-lg-6">
    <div class="input-group">
      <div class="input-group-btn">
        <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown">Action <span class="caret"></span></button>
        <ul class="dropdown-menu">
          <li><a href="#">Action</a></li>
          <li><a href="#">Another action</a></li>
          <li><a href="#">Something else here</a></li>
          <li class="divider"></li>
          <li><a href="#">Separated link</a></li>
        </ul>
      </div>
      <input type="text" class="form-control">
    </div>
  </div>
  <div class="col-lg-6">
    <div class="input-group">
      <input type="text" class="form-control">
      <div class="input-group-btn">
        <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown">Action <span class="caret"></span></button>
        <ul class="dropdown-menu pull-right">
          <li><a href="#">Action</a></li>
          <li><a href="#">Another action</a></li>
          <li><a href="#">Something else here</a></li>
          <li class="divider"></li>
          <li><a href="#">Separated link</a></li>
        </ul>
      </div>
    </div>
  </div>
</div>