If you're looking for the solution, head over to the official Bootstrap page where you can find it: Bootstrap Spacing Classes
The naming convention for the classes follows this pattern: {property}{sides}-{size} for xs, and {property}{sides}-{breakpoint}-{size} for sm, md, lg, xl, and xxl.
The properties include:
m - for margin classes
p - for padding classes
The sides include:
t - for margin-top or padding-top
b - for margin-bottom or padding-bottom
s - (start) for margin-left or padding-left in LTR, margin-right or padding-right in RTL
e - (end) for margin-right or padding-right in LTR, margin-left or padding-left in RTL
x - for both left and right margins or paddings
y - for both top and bottom margins or paddings
blank - for setting margin or padding on all 4 sides
The sizes include:
0 - to eliminate margin or padding
1 - sets margin or padding to $spacer * .25 by default
2 - sets margin or padding to $spacer * .5 by default
3 - sets margin or padding to $spacer by default
4 - sets margin or padding to $spacer * 1.5 by default
5 - sets margin or padding to $spacer * 3 by default
auto - sets margin to auto