What is the difference between the passé composé tense and the imperfect in french

There are two crucial differences between the two tenses, the first being when you use it and secondly how you form each of them.  The passé composé is COmposed of two parts of verbs, for example j'ai fait, I did/have done. This can be used for a snapshot of something that you did in the past, j'ai fait la table, I made or have made the table. It is a moment in the past where you did something. The imperfect tense however, is formed using only the pronoun je and the verb faire conjugated into the imperfect tense, ie. it does not use a complementary verb like avoir or etre. The imperfect tense could be used to describe a time where you were making the table when something happened - je faisais la table quand elle est entrée. Here the woman entered at a specific moment, hence the use of the passé composé, whilst you were doing something over a period of time, think of a video compared to a photograph, both taken in the past.