what is the difference between didn't and don't

didn't is a negative past form of do. did not = didn't don't is negative form of do. do not = don't

Didn't is used in simple past tense for forming a negative sentence. Ex:- I didn't have a car. Don't is used in simple present tense for forming a negative sentence. Ex:- I don't have a pen. Don't is also used in imperative sentence for forbid to anyone for doing any work. Ex:- Don't go out. Don't pluck these flowers.