Based on bootstrap 4 grid & based on 1170 px grid system

Hi i have a question what is that mean : based on bootstrap 4 grid and and based on 1170 px grid system ? and thanks in advance

Bootstrap is framework allows you to create website fully responsive option. You can check the website for details

i know but what is that mean based on 1170 px grid system ?

You know getbootstrap ! But don’t 1170px mean ?
1170px Mean Container Wide 1170px

You can take a look on getbootstrap.

Thanks