It is a tool designed to allow people to show disagreement with some aspect of the post however is often used as a tool attack others also, which is a shame.

Let's say someone was abusing the reward pool by self-voting on their very bad content 10 times a day, every day and was receiving no engagement on those posts. That is called reward-pool abuse and would attract downvotes.

The downvote returns any reward to the reward pool so that others can benefit from it rather than that other account raping the rewards for themselves.

The downvote is designed for the community to address issues as a whole, to remind those abusing the system that that sort of behaviour affects us all negatively and that it will not be tolerated.

However, some use it to retaliate, to attack and just for fun, which I don't think is the right way to go.

Does this help. Do you have any other questions?