What does "stacks" mean here? I've seen it in a few comparison sheets and I don't really understand it. Seen it in regards to artifacts as well.
You should read the passive effects on those weapons. On the Serpent Spine for example: "Every 4s a character is on the field, they will deal 6% more DMG and take 3% more DMG. This effect has a maximum of 5 stacks and will not be reset if the character leaves the field, but will be reduced by 1 stack when the character takes DMG."