Soldering irons and soldering guns are not interchangeable. These are two very different types of tools, mainly based on heat output and its control. A soldering gun has no real heat control other than pressing and releasing the button that engages the heating element. It's easy to forget and damage a delicate piece of work in the beginning stages of your soldering experience.
A soldering iron can be purchased with no heat control, all the way up to thermostatic control for those who want to vary the heat of the soldering tip depending on the needs of the job. Soldering irons come in a variety of wattages. Some recommend low wattage (between 15 and 30 watts) for small jobs such as circuit boards, and larger wattage (40 or more) for big jobs like soldering audio connections. Don't bother trying to use a soldering tool for a truly large project such as plumbing work, where a blow torch is definitely the right tool for the job.