Thank you for your answer! But i have one question. Per what you said, "work at" can be replaced by"work for" , and vise versa. So there is no difference at all between the two? For example, " I work for an accounting company." / " I work at an accounting company." They are exactly the same meaning? – More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.