To hearing vs to hear

[Mr Francis]

Hello,

I would like to know why the following sentences have the verb "to hear" in different forms:

1- I look forward to hearing from you;
2- It was so great to hear from you.

Thanks a lot in advance. Cheers!
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[Luschen]

I don't know the answer, but if you post this on the grammar and idiom forum, someone there is sure to know.

[Mr Francis]

I just did. Thank you.
_________________
You can get it if you really want.