I am quite new to OS X and I have just discovered a fantastic Python IDE, which is PyCharm. The problem is that every time I want to start it, I need to click on its installer, which apparently is also its 'runner'. PyCharm looks a lot like some Eclipse versions in this sense.
Also, why does some software does not need to be installed before being executed, for example PyCharm? Or, if you prefer, why software needs to be installed?