Hai, genki desu means "Yes, I am fine" or "Yes, I am well." This is a common and polite response to the question "Ogenki desu ka?" It indicates that you are doing well and in good health. It's often followed by asking about the other person. "はい、元気です。あなたは？" (Yes, I'm fine. And you?).

「お元気(げんき)ですか」と聞(き)かれた時(とき)の肯定(こうてい)的(てき)な返事(へんじ)です。体調(たいちょう)が良(よ)いことを伝(つた)えます。「はい、元気(げんき)です！」