I need help understanding the coding behind this kind of problem.

Welcome to the fruit database! Do you want to (A)dd, (D)elete, (S)how the list or (E)xit? A Enter a fruit: apple Do you want to (A)dd, (D)elete, (S)how the list or (E)xit? A Enter a fruit: banana Do you want to (A)dd, (D)elete, (S)how the list or (E)xit? A Enter a fruit: cherry Do you want to (A)dd, (D)elete, (S)how the list or (E)xit? S apple banana cherry Do you want to (A)dd, (D)elete, (S)how the list or (E)xit? D Enter the fruit to delete: apple Do you want to (A)dd, (D)elete, (S)how the list or (E)xit? S banana cherry Do you want to (A)dd, (D)elete, (S)how the list or (E)xit? A Enter a fruit: watermelon Do you want to (A)dd, (D)elete, (S)how the list or (E)xit? S banana cherry watermelon Do you want to (A)dd, (D)elete, (S)how the list or (E)xit? E Goodbye!