Checklist configuration, Action URL and Notes

Summary

what is the purpose of Action Type in the checklist task configuration and also Note

Content

Hi,

When trying to give the  External URL under Action Type, it is not pointing to the correct URL,  like we are giving our onedrive link but not able to open. any idea what might be the mistake or how the url should look like? 

When gave the word doc after selecting the Document, under Action Type, this document is not getting reflected anywhere (my understanding is it should get as an attachment in the email to performer) 

What is the purpose of "Notes" under Task?