What is the basic or general idea of the ke event?

It is a competition between players in your Province to see who can get the most kills of enemy player units there are rewards for the top players with the top kills. Most high level players will participate and they generally attack anyone they can unless there are province rules like NAP Alliances (Non attackable players). Best bet if you are lower levels are to use peace shields during the event to keep yourself protected or to join a high level alliance. It goes from Start of Day Saturday to end of day Sunday. The Game mods usually inform us via the messages when these events will occur. They do not happen every weekend.