First of all you should ask yourself why would you want something, which you have no idea of what it is. This is not meant as an offense, but rather as an advice to make sure you know what you want.
Other than that: I think what you are looking for is a DAW. It's a studio software. Basically a digital studio packed into a software package. There are quite a few: Garage Band (not fully featured, but cheap for what you get), Logic Pro (fully featured, good for it's price, mac only as well), Ableton Live (my personal preference, nice hardware integration with "Ableton Push', not the cheapest though), ProTools (don't know too much about it), FL Studio (popular since Avicci and Martin Garrix use it), Bitwig (was released just this week. looks very promising, but not testet yet)
You won't have to get a MIDI-keyboard, but it helps. Also pads, knobs etc. Basically all those things are just controllers so you CAN do it all with your mouse, but it of course gets easier with some equipment.
If you are a bit more serious about producing you will want studio monitors and a decent audio interface.
Well apart from a DAW, monitors and an audio interface (and maybe room treatment) what makes the professionals professional is knowledge so... try, learn, error, keep trying and most important have fun.
Some good things to start from: Download any DAW demo version (limited in time or function, but free), which almost every DAW offers. Just have a look at
https://www.ableton.com/en/trial/ or
https://www.bitwig.com/en/bitwig-studio/download.html or
http://www.image-line.com/downloads/...odownload.html .
Once you downloaded one or two of them try them on your own, with the help of youtube tutorials or just the manual.
If you have any question: ask.
By the way: Don't expect to have result within the first month. It took me four weeks of daily practice until I thought I had my first song created, a few month till my girlfriend said: "That's your first actual song." and even longer if you want a result that comes close to what you wanted when you started.
But that doesn't mean It's not fun, so practice and enjoy

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