It's how people would find your club when they 検索 words または phrases. The キーワード should be relevant to the club.
Say あなた made a smiley face club. (First thing that popped to mind.) あなた might make the キーワード things like "happy" and "smiles" and "emoticons." So whenever someone searched happy, smiles, または emoticons, your smiley face club would 表示する up as a result.
