Sometimes, you want an application to start up immediately every time you log in. Alternatively, sometimes you have too many applications doing that and booting up your computer becomes impossibly slow. In Windows, managing the registry and the various startup folders can be a handful, but Mac OSX offers a clean single place where all programs that launch upon startup are managed. You can access these settings by going to System Preferences -> Users&Groups -> Login Items:

This provides a clean, simple interface where you can manage what does or does not get launched at startup. To add or remove programs from this list simply click the + or - signs on the bottom left, and if you want a program to launch invisibly upon startup check the "Hide" box, which will run it in the background and not show it on the Dock.