Containers
They contain things.
.container-s (640px)
.container-m (960px)
.container-l (1280px)
.container-full-width (100%)
Bootstrap Containers
For the grid system, use .container
for making rows with a responsive fixed width or .container-fluid
for a full width container that spans the entire width of your viewport.
.container (1212px)
.container-fluid (100%)