Pistol question

I have a hard time understanding pistols. It says in the rules, that you can use them in melee using Ranged modifier - that is clear. But then it is added that you can use them as an off hand melee weapon, and that confuses me. So do I normally just shoot pistols in melee, and then later have an option to melee with them? Or is shooting in melee treated as melee attack from the very beginning? So for example, when in melee range, can I shoot an autopistol twice, and then hit the foe with my sword and a pistol stock in off hand?