Thank you for taking the time to post a plea.
Your ban was a three day temporary ban for killing someone's farm animals. Killing animals that are claimed by another player (as denoted by them being in an animal pen that you did not build, which these were) is considered griefing. Griefing can be many things, such as killing another player's animals, destroying another player's buildings, and even stealing their crops from their farms. Griefing is not tolerated on Famcraft.
I have unbanned you but I should let you know that if you are caught doing stuff like that again, the punishment will be more harsh.