Jmat has pretty much hit the nail on the head, except for some minor details. 東 is a Traditional Chinese character and 东 is a Simplified Chinese character. Simplified Chinese was created in the 1950s. Today, it is only used in Mainland China and Singapore. Hong Kong and Taiwan still use Traditional Chinese to this day. The only purpose of Simplified Chinese is to make Chinese easier to write, and that's literally the only difference between Simplified and Traditional Chinese. They are just 2 different writing standards. Sometimes people ask me whether I *speak* Simplified Chinese or Traditional Chinese, and that's not a valid question. I speak Mandarin, and I *write* Simplified Chinese. Personally, I cannot write Traditional Chinese, but I have little trouble reading it. In terms of interchangeability, I don't think I have an answer for you, because the question itself doesn't make a lot of sense. Let me explain why. For example, the word "color" is spelled "colour" in the UK and "color" in the US. Kind of like 東 and 东, "color" and "colour" are just 2 different ways to write the same word. So do you think "color" and "colour" are interchangeable? In my opinion, the question is meaningless, because no one will ever attempt to "interchange" them. American people will always write "color" and British people will always write "colour", but everyone can recognize both "color" and "colour".

They're the same character and the same word, but the former is written in traditional script and the latter is written in simplified script. Traditional characters are used in all Chinese texts written before 1946 (when simplified characters were invented in the PRC to improve literacy), or in modern day Hong Kong or Taiwan. China and Singapore use simplified characters.

they are a same character, one is ancient character, the other one is modern character.

Well, their answer sucks. Let me tell the difference. 東 is less often used, but they can be widely seen in some very limited part of China, like Taiwan. However, they CAN be seen in other part of China, for example, one of my classmate's name contains this character. Honestly, at first I got a bit puzzled about it cuz it's really weird to be found in many part of China, but then I got used to it and it doesn't bother me really. 东, however, it widely used in China cuz it's simplified, we use it in our daily basis instead of the former one. So you only have to remember this and forget the former one. One little tip for you to learn Chinese: If possible, try to know whether a character has been simplified or not. If not, forget it as soon as possible, cuz we almost never use that weird character, we use simplified! There's no need at all to learn the ancient Character( not multiplied one), it's nothing but a waste of time and cause a lot of problem. Hopefully my answer would be helpful. Peace!

东-CHS (USE IN MAINLAND,WRITING FORM,LIKE,东方） 東-ZH-HK（USE IN HK,WRITING FORM，LIKE,東方) PRONUNCIATION：SAME（东方/東方 means EST，JUST DIFFERENT WRITING FORM）