YES! SQL database take backup offline BUT there are two conditions how to represent OR bind data from database in the web page:
Database connected to the Server (Needs Internet connection)
When we run a website page on-localhost but database connected to the server in this condition we can easily bind OR show the data on the page.
The second condition (Internet disconnected)
In this situation, we are not able to bind the data from the database on the localhost page run because of internet connection actually SQL server needs to connect to the project.