A postcard — a postal card for writing an address and message (sometimes can be sent without a stamp), including items like New Year's postcards.
旅行先から家族に郵便はがきを一枚出した。
I sent a postcard to my family from my trip.
郵便はがきには宛先と差出人の住所を明記してください。
Please clearly write the recipient's and sender's addresses on the postcard.
年賀状は通常、郵便はがきに写真やメッセージを印刷して送る。
New Year's cards are usually printed with photos or messages on postcards and sent.