xs = Extra small <576px
Max container width None (auto)
sm = Small ≥576px
Max container width 540px
md = Medium ≥768px
Max container width 720px
lg = Large ≥992px
Max container width 960px
xl = Extra large ≥1200px
Max container width 1140px
Source : https://bootstrapcreative.com/bootstrap-4-media-queries/