Explain details Basic Progress Bar of Bootsrap

Basic Progress Bar

A progress bar can be used to show a user how far along he/she is in a process.
Bootstrap provides several types of progress bars.
A default progress bar in Bootstrap looks like this:

70% Complete

To create a default progress bar, add a .progress class to a <div> element:

Example

<div class="progress">
  <div class="progress-bar" role="progressbar" aria-valuenow="70"
  aria-valuemin="0" aria-valuemax="100" style="width:70%">
    <span class="sr-only">70% Complete</span>
 </div>
</div>
Very important  Note: Progress bars are not supported in Internet Explorer 9 and earlier (because they use CSS3 transitions and animations to achieve some of their effects).

Very important  Note: To help improve accessibility for people using screen readers, you should include the aria-* attributes