「円」(en) means "yen," which is the official currency of Japan. You always place "円" after the number when stating an amount of money. For example, 「五百円」(gohyaku-en) means "five hundred yen." It's essential for transactions.

「円(えん)」は日本(にほん)の通貨(つうか)単位(たんい)です。金額(きんがく)を表(あらわ)す時(とき)に数字(すうじ)の後(あと)に付(つ)けます。例(れい)：「五百円(ごひゃくえん)」。