Credit: recognition by a school or college that a student has fulfilled a requirement leading to a degree

كريدت: قبول رسمى لنتائج عمل الطالب فى حقل من الدراسة و تدوين ذلك فى سجله

Pass, credit, distinction and high distinction indicate how well you did in an exam. Basically, the difference lies in how well you have achieved the demands of the assessment task your lecturer has set for you. A pass indicates you've done the minimum, enough to just meet the needs of the task; a HD indicates you've done a great job and perhaps exceeded expectations.

60%-69% pass = C = you've barely made it.
70%-79% credit = B = good
Above 80% DISTINCTION = A = excellent.