Answer: there are many forms of communism and fascism (!!!) Italian fascism is not the same as English or Romanian fascism. Differences exist especially in theory, ideology, doctrine. When we move to practice and regime as it works in reality, there are few differences (for example: Communism should be theoretically open to all people without discriminating race....in the USSR Jews were discriminated). So description of differences will be purely theoretical:
1) fascism is born around 1900 whereas Communism came into existence (as a theory) already in 1848 (Communist Manifesto by Karl Marx).
2) Communism has its central authority (Karl Marx)....all the rest is derived from his thought. Fascism lacks that....it is a nebulous plurality of authors, mixture of ideas.
3) Communism is product of Enlightenment (primacy of reason, idea of progress, just society etc.) whereas fascism is a produt of Anti-Enlightenment (irrationalism, primacy of ancestry or race, belief in the soul of nation, sometimes necessity of exceptional leading elite, frequently is linked with some almost religious faith, cult of body, physical strength, very patriarchal, references to Middle Ages).
Explanation: similarities....both were born in times where masses were entering politics and both needs masses. Both preach man of masses. They do not promote individuality, individuality is suppressed.