Text Editor vs. Notepad
You've probably realized you can write or edit files with a program similar to Windows Notepad.
What you don't know is that you need to learn how to use a text editor before you can really program.
Text Editing vs. Word Processing
Think of all the bells and whistles that goes into something like Microsoft Word or Libre Office. All that work into making a program that makes it easy to write a beautiful document is easily underestimated.
Now, imagine trying to put together a document with something like Notepad. Sounds impossible, doesn't it? That's how people who are experienced with text editors feel about writing programs in Notepad.
The comparison is apt: It's really hard to put together a beautiful document. It's just as hard to put together a beautiful program.
Which Text Editor?
All of them are really decent. My preference is ViM. It has a steep learning curve, but it is well worth the effort.
Others prefer Emacs, although I feel like I code much faster than them in ViM. I haven't worked with anyone who uses a text editor other than emacs or vim.
Still others use whatever pathetic excuse for a text editor comes with their favorite IDE. I pity them.