Grid System

Always Horizontal

Equally distributed across all devices automatiaclly
.col
Four columns across all devices
.col-3
Three columns across all devices
.col-4
Two columns across all devices
.col-6
Single columns across all devices
.col-12

Mixed Columns

.col-md-6 .col-lg-4

Column wrapping

.col-9
.col-4
Since 9 + 4 = 13 > 12, this 4-column-wide div gets wrapped onto a new line as one contiguous unit.
.col-6
Subsequent columns continue along the new line.

Offsetting columns

.col-md-4
.col-md-4 .offset-md-4
.col-md-4 .offset-md-4
.col-md-4 .offset-md-4
.col-md-6 .offset-md-3

Vertical alignment

One of three columns
One of three columns
One of three columns

Horizontal alignment

One of two columns
One of two columns
One of two columns
One of two columns
One of two columns
One of two columns
One of two columns
One of two columns
One of two columns
One of two columns

Example

Column 1

Lorem ipsum dolor sit amet orem ipsum dolor sit amet consectetur, adipisicing elit.

Column 2

Lorem ipsum, dolor sit amet consectetur adipisicing elit. Lorem ipsum, dolor sit amet consectetur adipisicing elit.

Column 3

Lorem ipsum dolor sit amet consectetur, adipisicing elit. Nesciunt maxime voluptate molestiae placeat minima facilis, natus corporis fugit voluptates

Column 4

Lorem ipsum dolor sit, amet consectetur adipisicing elit. Nesciunt maxime voluptate molestiae placeat minima facilis, natus corporis fugit voluptates

For complete information on Bootstrap 4 Grid system : Bootstrap 4 Docs launch