The Bootstrap grid system is based on how many columns? code example
Example 1: bootstrap screen sizes
The Bootstrap grid system has four classes:
xs (for phones - screens less than 768px wide)
sm (for tablets - screens equal to or greater than 768px wide)
md (for small laptops - screens equal to or greater than 992px wide)
lg (for laptops and desktops - screens equal to or greater than 1200px wide)
Example 2: row class in bootstrap
<div class="row">
<div class="col-md-6"></div>
<div class="col-md-4"></div>
<div class="col-md-2"></div>
</div>
Example 3: a column inside another column bootstrap html
<div class="row">
<div class="col-sm-9">
Level 1: .col-sm-9
<div class="row">
<div class="col-8 col-sm-6">
Level 2: .col-8 .col-sm-6
</div>
<div class="col-4 col-sm-6">
Level 2: .col-4 .col-sm-6
</div>
</div>
</div>
</div>