Diablo II/Classes

Skills are what make your character in Diablo II. A Sorceress wouldn't be a Sorceress without the ability to summon the elements to her finger tips; in the same respect a Barbarian wouldn't be the same if he couldn't wield mighty axes and swing them as if they were nothing.

Each character type's skills are set up into three trees. Every tree focuses on a different set of skills, for example Amazons have a tree that focuses on Bow and Crossbow skills, in which every skill affects the usage of bows and grants the Amazon powerful abilities to unleash on her enemies.

The skills that are chosen and focused upon are what make your character; for example by choosing mostly fire skills as a Sorceress, you become deadly with that element while weak with others. Your choice of skills is your "build." Character builds are what determine how you will play the game and what your strengths and weakness are. Usually trying to have a broad focus of skills, i.e. using all three skill trees will end up making your character a jack of all trades and weak in every respect rather than strong in one, and weak in another. Remember that at a higher difficulty, monsters will have immunities and thus single tree/element strengths will fail while double or multi will be successful.

It all comes down to either your experience within the game, or the "pre-work" that you do to understand what will be best for you and your character.