Classes : lots
The .input-group class is a container to enhance an input by adding an icon, text or a button in front or behind it as a "help text".
The .input-group-addon class attaches an icon or help text next to the input field.
It can also be used on the right side of the input:
The .input-group class is a container to enhance an input by adding an icon, text or a button in front or behind it as a "help text".
The .input-group-btn class attaches a button next to an input field. This is often used as a search bar: