beginner for robotics , how to use what program

I am a beginner.
What languages are used to program arduino?
and where on what platform?
what do we install where and then in what computer language we write?
as i said i am complete beginner and have no idea. please do not direct me to a 1 million page reference. I only need your 5 sentence answer that is all.

Windows PC, Mac, Linux
Install the IDE (software) on the PC, program in C++, download to an Arduino board (hardware)

Thanks and on the link you gave I saw a web editor or the download version, they both do the same thing and one is on the web and one is for installing on to the computer?

Also, I had installed Visual Studio on my laptop, it writes Visual C++ I think is this ok too or I need to install something and it needs to be C++? I ask because I am also beginner for C++