An ipython interpreter has certain nice-to-use features that provide more ease of use. It has syntax highlighting, file navigation/system commands that can be easily run inside the console, magic commands like %edit to access special features, tab completion etc.

The main difference is that IPython is IPython notebook. You can put all your work into a notebook like script, image files, etc. But with normal python interpreter, you can only make the script in a file and execute it.