Desktop vs Mobile coding (specially in web coding)

Question

I am learning html,css by vs code on desktop,
Now sometimes I am using my mobile or sololearn app in mobile,
I need to know what is the difference between
(I think I am confused in responsive websites coding)
Like when we code in desktop we need to make web responsive
But when we code in mobile then what is the difference?

Answer 1

Thank you
For giving me such a good advice also I am using otg connecter to connect keyboard to my anroid phone not for build over all web page like hosting is not done on my mobile phone ,moreover the whole website would be ready upon coding