Which is the best way to start coding in ASP.NET

Question

Sir, I am doing training in .Net.

Here is my doubt:-

My tutor told us to write the ASP.Net code using Notepad in the beginning time of ASP.NET training.

Why we write in that way as we have  tools like visual Studio ?

what is the difference  in writing the ASP.Net code in Notepad and Visual Studio?

please let me know?