Do I need an external host?

I’m a newbie and trying set up a simple blog to get started.
I’ve been all over the installation instructions and other pages and to be honest I just don’t understand them.

Do I need an external web host? I can’t get a simple straight answer to this, there are times that the instructions infer that I do and there’s times when other pages seem to contradict this.
I don’t have my own web site and I really don’t want to set one up.

Thanks in advance.