What is the difference between to+verb and to+verb-ing

can someone please tell me when should I use to+verb and when to use to+verb-ing?
Which one is correct:

  1. I’m looking forward to hear from you
  2. I’m looking forward to hearing from you
    In the test I’ve, the second answer is the correct one, but why?
    Thanks alot for your help…

Looking forward to is followed by a noun, not a verb. That’s why you need ‘hearing’, not ‘to hear’. By the way, ‘a lot’ are two separate words.[YSaerTTEW443543]

TOEFL listening lectures: Why does the professor mention Mona Lisa?[YSaerTTEW443543]