"قد" is a character enters the verbs only.when it enters the past tense, it indicates the occurrence of the act or near the occurrence of the act,for example: قد غربت الشمس قد قامت الصلاة and When it enters the present tense, it indicates the abundance of the act, or the lack of the act ,for example: قد يفعل التقي الخير قد يجود البخيل بماله

when you are very sure of something happened in the PAST, you can say it;e.g. قد أكل طعامه meaning= he has eaten his meal. but when you are not sure of somthing that will happen in the FUTURE, you can also say it; e.g. قد يأكل طعامه meaning= he may eat his meal.

"قد" denotes the past,, ex: was gone {قد ذهب} ex: he was sick{فقد كان مريضا }