Mathematica is meant to be used interactively. An IDE is only useful if you are writing big and complex packages and is completely unsuitable for day-to-day work with Mathematica. If you are a beginner, you won't be writing packages for a while. It is not the usual (or IMO the productive) way to use Mathematica.
Perhaps you are used to working this way in other languages:
- First type the code in a file. This is often a large program/scipt.
- When done, run it.
- Edit the code, re-run, etc.
Mathematica uses the notebook interface instead. You evaluate a small input and see the output immediately. Then tweak it. Move to the next small input. Go back to previous ones, edit them, etc. You re-run a small piece of code after each edit and you see the result.
The structure of the language is such that is it very suitable for working interactively like this.
Typical stuff that people do with Mathematica, such as scientific data processing, also benefits significantly from the notebook interface.
Mathematica was a pioneer of the notebook. Then notebooks became standard in computer algebra systems, but not with other high level scientific languages. Finally in the past 5-10 years people started to see the great benefits of the notebook paradigm and the most prominent scientific programming languages all use it now. MATLAB had "cell mode" first (years ago), which is really just borrowing a few great features of notebooks, and finally introduced the "Live Editor" which is a full notebook interface.
IPython, the Python shell for scientific work, also has a very good, web based notebook. This morphed into the Jupyter project, which works with many other scientific languages, such as Julia.
The only such system I am familiar with where the notebook is not yet popular is R. It has something they call notebooks, but it's something entirely different and meant for report writing, not for interactive work. But several R environments, such as RStudio, have borrowed features of MATLAB's cell mode.
So as you can see, the notebook is becoming a standard interface for the type of work Mathematica is meant for. Forget about IDEs for a while and try it.