Is there an imperfect tense in English? If so, what is the difference between the perfect tense and the imperfect tense?
Yes. Perfect tense uses the word 'have' before the past participle, while imperfect uses only the imperfect conjugation.
The perfect tense uses an auxiliary verb and the past participle, while the imperfect tense uses only the imperfect conjugation of the verb.
Perf: 'I have been'
Imperf: 'I was'
Here 'have' is the auxiliary verb and 'been' is the past participle. 'Been' is also called the lexical verb because it carries the real meaning of the sentence, while 'have' just specifies the time period in which it happened - the past.
More examples are
Perf: I have gone, I have looked, I have seen, I have played, I have kicked, I have disappeared, I have given, I have had
Imperf: I went, I looked, I saw, I played, I kicked, I disappeared, I gave, I had
You can see that often the past participle and the imperfect conjugation are the same, though in some common verbs (to be, to see, to go) they are different.
You can also translate the imperfect tense into English as 'I used to..' or 'I was... -ing'. These are still imperfect because they use the imperfect conjugation of 'to be' or 'to use' (was, used) plus either the infinitive or gerund of the verb.