The Witcher weapon system:
You get your Steel Sword from the start, the steel sword is most effective against humanoids. At a certain point in the game you will get your Silver Sword, silver swords are most effective against monsters. These two will be your primary weapons.
During the game you will encounter other weapons such as Axes, Daggers, Torches and also other swords. These can be equiped in your 2 extra weapon slots. I almost never use these weapons, but in some situations they can come in quite handy(the Torch deals almost no damage, but is a good light source in dark spaces, disabling the need of a Cat potion). Each weapon is used individually so you don't actually dual wield the swords. In fact both Swords are used as 2-handed weapons, altough you can change your weapon during combat, your combo sequence will be broken if you do.