Bootstrap Grid is used to create fluid layout uses a series of containers, rows, and columns to layout and align content.
In these example the html layout can look as follow.
<style>
.box{
display: block;
position: relative;
width: 100%;
height: 200px;
}
.left{
float: left;
}
.right{
float: right;
}
</style>
<div class="row">
<div class="row">
<div class="col-sm-6 box">
</div>
<div class="col-sm-6 box"></div>
</div>
<div class="row">
<div class="col-sm-8 right box">
</div>
<div class="col-sm-8 right box">
</div>
<div class="col-sm-4 left box">
</div>
</div>
<div class="row">
<div class="col-sm-12 box">
</div>
</div>
</div>