Technically, there is no difference! Just two different ways to say it. :)

下面的回答有错误。"every other day" is not necessarily "every two days," though it can be. 比如说：如果我三天以前打了网球，今天打了网球，四天以后又打了网球，我可以说："I play tennis every other day." 所以“every other day"的意思就是“经常，可是不是每一天做的“。