Standard term for a postcard, especially one issued by the post office.
旅行先から郵便はがきを送った。
I sent a postcard from my travel destination.
郵便葉書 is the full official postal term for a postcard, while 葉書 is the everyday abbreviated form used in casual speech.
Standard mixed kanji-kana spelling.
Full kanji spelling; less common but still seen.
Compound of 郵便 (postal service) and はがき (postcard).