There are many weapon items in the game but they are all very similar - weapons are used offensively to kill mobs. (You will find that this page is very similar to the page on Defenses ... and that should not be a surprise.)
As a single Player, we each have two "characters". Each of them has a number of "slots". There is only one weapon slot. The rest are for defensive items and abilities. The weapon slot can accept items like:
The weapons all have very creative names, but these are not important.
What is important is the Damage level. Weapons hit within a range, based on their level. When used, the hit points against the target mob is random, somewhere in the defined range. For example, a level 19 item might have a damage range between 50 and 130, while a level 23 item might have a range of 70 to 170. The higher the level, the more damage the weapon inflicts. This is one reason why we want to get to higher levels. We can't use a level 23 item until our player/characters reach level 23.
Another factor that affects weapon damage is the tier. Poor items hit for less than Common items. Rare items hit for less than Legendary, etc. This is not always the case, it's a generalization. For example, A Common item might also have bonus Character Attributes, like Vitality. Because it has a separate bonus, it might hit for less damage. We get a little more here, and a little less there. Epic and Legendary items have a lot of attribute bonuses. Their damage level is usually very high, but not always if there are good attribute bonuses.
Rings and necklaces can be thought of as weapons. While not active weapons, they are "energized" with Character Attributes like Power, Dexterity, and Luck, to help increase the value of the weapons. The Character Attributes can be very important when combined with weapons. For example, the Power level increases the damage inflicted by the weapon. Dexterity increases the chance of making a "critical hit", which is a high level hit that is very likely to kill a mob. While Luck doesn't affect the hit points directly, luck is like dexterity in that it does increase the chance of getting a critical hit.
While it's always nice to be able to hit with the highest possible hits, some weapons with a lower hit range are preferable because of their bonuses. Experiment and decide what you prefer - higher hits or more bonuses. You might decide to hold on to a lower level weapon with less damage simply because of the bonuses.