Bootstrap 4 grid, column layout col md offset, and more

Hello everyone, this is my first question on stukoverflow, and so, I'm learning layout using bootstrap 4, and it uses grid technology, my mentor somehow magically when creating a container disposes everything using col md and values, I of course understand that here are 12 columns there are all contained inside them and positioned accordingly, but I don't understand a little how it works, all the Bootstrap documentation is in English, and English I have but sow perfect to understand everyone, please explain in an accessible language how it works. Ps I have a good mood today, please, people with a bad mood/sense of humor, do not pay attention to the humorous subtext.