Hi Diana, I think the answer is less clear-cut than Joao suggests. 'Right now' can be used of a longer time period too, and 'at the moment' can refer to a brief instant. After all, 'moment' really means a brief instant! So as a native speaker, I would say the two expressions are interchangeable.
Note: you need to say 'what is the difference' not 'what is the different'.
Hope this helps!