It's called "open at login" and can be found by simply right-clicking the icon when it is in your dock (ie, when open), choose "Options" and selecting "Open at login." From then on, the item will launch on every reboot, restart or login. You can turn the option off if desired by repeating this action.
Alternatively, you can also open Users & Groups in System Prefences (might be called "Accounts" on non-Mavericks versions of the OS), click on the "Login items" tab, and add what you want there. Same effect.